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A History of Planetary Radar Astrononr 



Andrew J. Butrica 



To See 

the 
Unseen 



A History of 
Planetary Radar Astronomy 



The past 50 years have brought forward a unique capa- 
bility to research and expand scientific knowledge of 
the Solar System through the use of radar to conduct 
planetary astronomy. This technology involves the aim- 
ing of a carefully controlled radio signal at a planet (or 
some other Solar System target, such as a planetary 
satellite, an asteroid, or a ring system), detecting its 
echo, and analyzing the information that the echo car- 
ries. 

This capability has contributed to the scientific knowl- 
edge of the Solar System in two fundamental ways. 
Most directly, planetary radars can produce images of 
target surfaces otherwise hidden from sight and can 
furnish other kinds of information about target surface 
features. Radar also can provide highly accurate mea- 
surements of a target's rotational and orbital motions. 
Such measurements are obviously invaluable for the 
navigation of Solar System exploratory spacecraft, a 
principal activity of NASA since its inception in 1958. 

Andrew J. Butrica has written a comprehensive and 
illuminating history of this little-understood but sur- 
prisingly significant scientific activity. Quite rigorous 
and systematic in its methodology, To See the Unseen 
explores the development of the radar astronomy spe- 
cialty in the larger community of scientists. 

More than just discussing the development of this 
field, however, Butrica uses planetary radar astronomy 
as a vehicle for understanding larger issues relative to 
the planning and execution of "big science" by the 
Federal government. His application of the "social 
construction of science" and Kuhnian paradigms to 
planetary radar astronomy is a most welcome and 
sophisticated means of making sense of the field's 
historical development. 

Andrew J. Butrica received his Ph.D. in the history of 
science and technology at Iowa State University. He is 
a research historian in Franklin Park, New Jersey, spe- 
cializing in the history of science. In 1990, Praeger 
Publishers issued his Out of Thin Air: A History of Air 
Products and Chemicals, Inc., 1940-1990. 

About the cover: "Big Dish Antenna" painting by Paul Arlt. 
Courtesy of the NASA Art Program, no. 74-HC467. 



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TO SEE THE UNSEEN 



NASASP-4218 



TO SEE THE UNSEEN 



A History of Planetary Radar Astronomy 



by Andrew J. Butrica 



The NASA History Series 




National Aeronautics and Space Administration 

NASA History Office 

Washington, D.C. 1996 



Library of Congress Cataloguing-in-Publication Data 

To See the Unseen: A History of Planetary Radar Astronomy / Andrew J. Butrica 
p. cm. (The NASA history series) (NASA SP: 4218) 

Includes bibliographical references and indexes. 

1. Planetology United States. 2. Planets Exploration. 3. Radar in 
Astronomy. I. Title. II. Series. III. Series: NASASP: 4218. 
QB602.9.B87 1996 95-35890 

523.2'028-dc20 CIP 



For sale by the U.S. Government Printing Office 

Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328 
ISBN 0-16-048578-9 



To my dear friends and former colleagues at the Center for Research in 

History of Science and Technology: Bernadette Bensaude-Vincent, 

Christine Blondel, Paulo Brenni, Yves Cohen, Jean-Marc Drouin, 

Irina and Dmitry Gouzevitch, Anna Guagnini, Andreas Kahlow, 

Stephan Lindner, Michael Osborne, Anne Rasmussen, 

Mari Williams, Anna Pusztai, 

and above all Robert Fox. 



Contents 

Acknowledgments iii 

Introduction vii 

Chapter One: A Meteoric Start 1 

Chapter Two: Fickle Venus 27 

Chapter Three: Sturm und Drang 55 

Chapter Four: Little Science/Big Science 87 

Chapter Five: Normal Science 117 

Chapter Six: Pioneering on Venus and Mars 149 

Chapter Seven: Magellan 177 

Chapter Eight: The Outer Limits 205 

Chapter Nine: One Step Beyond 225 

Conclusion: W(h)ither Planetary Radar Astronomy? 259 

Planetary Radar Astronomy Publications 267 

A Note on Sources 269 

Interviews 271 

Technical Essay: Planetary Radar Astronomy 275 

Abbreviations 287 

Index 289 

About the Author 297 

The NASA History Series 299 



From Locksley Hall 



For I dipt into the future, 

far as human eye could see, 

Saw the Vision of the world, 

and all the wonder that would be; 

Saw the heavens Jill with commerce, 

argosies of magic sails, 
Pilots of the purple twilight, 

dropping down with costly bales; 

Heard the heavens fill with shouting, 

and there rained a ghastly dew 

From the nations' airy navies 

grappling in the central blue; 

Far along the world-wide whisper 

of the south-wind rushing warm, 

With the standards of the peoples 

plunging through the thunder-storm; 

Till the war-drum throbbed no longer, 

and the battle-flags were furled 

In the Parliament of man, 

the Federation of the world. 

There the common sense of most 

shall hold a fretful realm in awe, 

And the kindly earth shall slumber, 
lapt in universal law. 

So I triumphed ere my passion 

sweeping through me left me dry, 
Left me with the palsied heart, 

and left me with the jaundiced eye; 

Eye, to which all order festers, 

all things here are out of joint: 

Science moves, but slowly slowly, 

creeping on from point to point: 

Alfred Baron Tennyson 
(1842) 



Acknowledgments 

Let me begin with a confession and some explanations. Before beginning this project, I 
knew nothing about planetary radar astronomy. I quickly realized that I was not alone. I 
discovered, too, that most people confuse radar astronomy and radio astronomy. The 
usual distinction made between the two is that radar astronomy is an "active" and radio 
astronomy a "passive" form of investigation. The differentiation goes much deeper, how- 
ever; they represent two disparate forms of scientific research. 

Radio astronomy is more akin to the methods of natural history, in which observation and 
classification constitute the principal methods of acquiring knowledge. Radio 
astronomers search the cosmos for signals that they then examine, analyze, and classify. 
Radar astronomy, on the other hand, is more like a laboratory science. Experimental 
conditions are controlled; the radar astronomer determines the parameters (such as fre- 
quency, time, amplitude, phase, and polarization) of the transmitted signals. 

The control of experimental parameters was only one of many aspects of planetary radar 
astronomy that captivated my interest, and I gradually came to find the subject and its 
practitioners irresistibly fascinating. I hope I have imparted at least a fraction of that 
fascination. Without the planetary radar astronomers, writing this book would have been a 
far less enjoyable task. They were affable, stimulating, cooperative, knowledgeable, and 
insightful. 

The traditional planetary radar chronology begins with the earliest successful attempts to 
bounce radar signals off the Moon, then proceeds to the detection of Venus. I have 
deviated from tradition by insisting that the field started in the 1940s and 1950s with the 
determination by radar that meteors are part of the solar system. Meteor, auroral, solar, 
lunar, and Earth radar research, as well as radar studies of planetary ionospheres and 
atmospheres and the cislunar and interplanetary media are specializations in themselves, 
so were not included in this history of planetary radar astronomy in any comprehensive 
fashion. What has defined radar astronomy as a scientific activity has changed over time, 
and the nature of that change is part of the story told here. 

This history was researched and written entirely under a contract with the California 
Institute of Technology (Caltech) and the Jet Propulsion Laboratory (JPL), as a subcon- 
tract with the National Aeronautics and Space Administration (NASA) . This history would 
not have come into existence without the entrepreneurial energies of JPL's Nicholas A. 
Renzetti, who promoted the project and found the money to make it happen. It is also to 
his credit that he found additional support for a research trip to England and for atten- 
dance at a conference in Flagstaff, as well as for the transcription of additional interviews. 
As JPL technical manager, he administered all technical aspects of the contract. I hope 
this work meets and exceeds his expectations. During my frequent and sometimes 
extended visits to JPL, Nick provided secretarial, telephone, photocopying and other 
supplies and services, as well as a professional environment in which to work. I also want 
to thank the JPL secretarial personnel, especially Dee Worthington, Letty Rivas, and Judy 
Hoeptner, as well as Penny McDaniel of the JPL Photo Lab, who was so resourceful in 
finding pictures. 



iii 



Teresa L. Alfery, JPL contract negotiator, deserves more than a few words of thanks. 
Working out the contract details could have been an insufferable experience, were it not 
for her. Moreover, she continued her cordial and capable performance through several 
contract modifications. 

The contract also came under the purview of the NASA History Office, which provided the 
author office supplies and services during visits there. More importantly, Chief Historian 
Roger D. Launius offered encouragement and support in a manner that was both profes- 
sional and congenial. It was a pleasure to work with Roger. This history owes not inconse- 
quential debt to him and the staff of the History Office, especially Lee Saegesser, archivist, 
who lent his extensive and unique knowledge of the NASA History Office holdings. 

I also want to acknowledge certain individuals who helped along the way. Before this pro- 
ject even began, Joseph N. Tatarewicz afforded it a rich documentary source at the NASA 
History Office by rescuing the papers of William Brunk, which hold a wealth of informa- 
tion on the Arecibo Observatory and other areas relevant to planetary astronomy at 
NASA. Joe also was a valuable source of facts and wisdom on the history of the space pro- 
gram and an invaluable guide to the planetary geological community. 

This history also owes a debt to Craig B. Waff. His extensive collection of photocopied 
materials greatly facilitated my research, as did his manuscript histories of the Deep Space 
Network and Project Galileo. Craig generously offered a place to stay during my first 
visits to California and was my JPL tour guide. 

The staff of the JPL Archives deserves an exceptional word of appreciation. They do not 
know the word "impossible" and helped facilitate my research in a manner that was always 
affable and competent. In particular, I want to acknowledge the director, Michael Q. 
Hooks, for assembling a superb team, John F. Bluth, for his command of the JPL oral his- 
tory collection and our informative talks about JPL history, and Julie M. Reiz, for her help 
in expediting access to certain collections. 

I also wish to thank those librarians, archivists, historians, and others who expedited my 
research in, or who provided access to, special documentary collections: Helen Samuels 
and Elizabeth Andrews, MIT Institute Archives and Special Collections; Mary Murphy, 
Lincoln Laboratory Library Archives; Ruth Liebowitz, Phillips Laboratory; Richard 
Bingham, Historical Archives, U.S. Army Communications-Electronics Command, Ft. 
Monmouth, NJ; Richard P. Ingalls and Alan E. E. Rogers, NEROC, Haystack Observatory; 
George Mazuzan, NSF Historian's File, Office of Legislation and Public Affairs, National 
Science Foundation; Eugene Bartell, administrative director, National Astronomy and 
Ionosphere Center, Cornell University; Jane Holmquist, Astrophysics and Astronomy 
Library, Princeton University; and August Molnar, president of the American Hungarian 
Foundation. 

In addition, I want to acknowledge those individuals who made available materials in their 
possession: Julia Bay, Bryan J. Butler, Donald B. Campbell, Von R. Eshleman, Thomas 
Gold, Paul E. Green, Jr., Raymond F. Jurgens, Sir Bernard Lovell, Steven J. Ostro, Gordon 
H. Pettengill, Nicholas A. Renzetti, Martin A. Slade, and William B. Smith. Credit also 
goes to those individuals who reviewed part or all of this manuscript: Louis Brown, Ronald 
E. Doel, George S. Downs, John V. Evans, Robert Ferris, Richard M. Goldstein, Paul E. 
Green, Jr., Roger D. Launius, Sir Bernard Lovell, Steven J. Ostro, Gordon H. Pettengill, 



IV 



Robert Price, Alan E. E. Rogers, Irwin I. Shapiro, Richard A. Simpson, Martin A. Slade, 
and Joseph N. Tatarewicz. 

There are numerous people at NASA involved in the mechanics of publishing who 
helped in myriad ways in the preparation of this history. J.D. Hunley, of the NASA History 
Office, edited and critiqued the text before he departed to take over the History 
Program at the Dryden Flight Research Center; and his replacement, Stephen J. Garber, 
helped in the final proofing of the work. Nadine Andreassen of the NASA History Office 
performed editorial and proofreading work on the project; and the staffs of the NASA 
Headquarters Library, the Scientific and Technical Information Program, and the NASA 
Document Services Center provided assistance in locating and preparing for publication 
the documentary materials in this work. The NASA Headquarters Printing and Design 
Office developed the layout and handled printing. Specifically, we wish to acknowledge 
the work of Jane E. Penn, Patricia Lutkenhouse Talbert, Kimberly Jenkins, Lillian Gipson 
and James Chi for their design and editorial work. In addition, Michael Crnkovic, Craig 
A. Larsen, and Larry J. Washington saw the book through the publication process. 

Finally, I want to recognize the friendship of fellow cat lover Joel Harris, the cordial and 
entertaining SETI evening spent at the Griffith Observatory with Mike Klein, Judy 
Hoeptner, and company (without forgetting the Renaissance Festival!), the stimulating 
conversations with Adrienne Harris, and the friendly folk dancers of Pasadena, as well as 
the contra dancers of Highland Park and Franklin Park, and Ghislaine, the most impor- 
tant one of all in many ways. 



Introduction 

Planetary radar astronomy has not attracted the same level of public attention as, say, the 
Apollo or shuttle programs. In fact, few individuals outside those scientific communities 
concerned with planetary studies are aware of its existence as an ongoing scientific 
endeavor. Yet, planetary radar has contributed fundamentally and significantly to our 
knowledge of the solar system. 

As early as the 1940s, radar revealed that meteors are part of the solar system. After the 
first detections of Venus in 1961, radar astronomers refined the value of the astronomical 
unit, the basic yardstick for measuring the solar system, which the International 
Astronomical Union adopted in 1964, and they discovered the rotational rate and direc- 
tion of Venus for the first time. Next, radar astronomers determined the correct orbital 
period of Mercury and calculated an accurate value for the radius of Venus, a measure- 
ment that Soviet and American spacecraft had failed to make reliably. Surprisingly, radar 
studies of Saturn revealed that its rings were not swarms of minute particles, but rather 
consisted of icy chunks several centimeters or more in diameter. Planetary radar also pro- 
vided further proof of Albert Einstein's theory of General Relativity, as well as the "dirty 
snowball" theory of comets. The only images of Venus' surface available to researchers are 
those made from radar observations. The ability of planetary radar astronomy to charac- 
terize the surfaces of distant bodies has advanced our general knowledge of the topogra- 
phy and geology of the terrestrial planets, the Galilean moons of Jupiter, and the aster- 
oids. The Viking project staff utilized radar data to select potential landing sites on Mars. 
More recently, radar revealed the surprising presence of ice on Mercury and furnished 
the first three-dimensional images of an asteroid. 

Again, these achievements seldom have attracted the attention of the media. The initial 
American radar detections of the Moon in 1946 and of Venus in 1961 attracted notice in 
daily newspapers, weekly news magazines, news reels, and cartoons. Only in recent years 
have the accomplishments of radar astronomy returned to the front-page of the news. The 
images of Venus sent back by Magellan received full media coverage, and images of the 
asteroid Toutatis appeared on the front-page of the New York Times. 

Planetary radar astronomy has shared its anonymity with other applications of radar to 
space research. The NASA radar-equipped SEASAT satellite provided unprecedented 
images of Earth's oceans; European, Canadian, and Japanese satellites, as well as a num- 
ber of space shuttles, have imaged Earth with radar. The radars of NASA's Deep Space 
Network also have played a major role in tracking space launches and spacecraft on route 
to planets as distant as Saturn and Neptune. Among the more down-to-Earth, visible and 
even pervasive applications of radar are those for air traffic control and navigation, the 
surveillance of automobile traffic speeds, and the imaging of weather patterns reported 
daily on television and radio. 

Planetary radar astronomy is part of the great wave of progress in solid-state and digital 
electronics that has marked the second half of the twentieth century. For instance, the ear- 
liest planetary radar experiment marked the first use of a maser (a solid-state microwave 
amplifying device) outside the laboratory. Although radio astronomy has long claimed the 
first maser application for itself, namely in April 1958 by Columbia University and the 
Naval Research Laboratory, two months earlier, MIT's Lincoln Laboratory used a maser 
in its first attempt to bounce radar waves off Venus. The same radar experiment also saw 



vii 



one of the first uses of a digital tape recorder, as well as the incorporation of a digital com- 
puter and other digital data processing equipment into a civilian radar system. 

The origins of this solid-state and digital electronics progress, as well as of planetary radar 
astronomy, are rooted in electronic research and development that started as early as the 
1930s. The first radar astronomy experiments, which were carried out on meteors and the 
Moon in the 1940s, relied on equipment designed and built for military defense during 
World War II and were based on research conducted during the 1930s. 

Planetary radar astronomy, and so too radar itself, had its origins in Big Science. British 
war preparations during the 1930s concentrated large amounts of scientific, technologi- 
cal, financial, and human resources into a single effort. Part of that effort was a massive 
radar research and development program that produced an impressive range of defensive 
and offensive radars. In a secret mission known only at the highest levels of government, 
Britain gave the United States one of the key devices born of that large-scale radar effort, 
the magnetron. In turn, the magnetron formed the technological base for an American 
radar research and development effort on a scale equal to that of the Manhattan Project, 
which historians traditionally have recognized as the beginning of Big Science. 

The history of planetary radar astronomy in the United States is the history of Big Science. 
Without Big Science, planetary radar astronomy would be impossible and unthinkable. 
That is one of the main contentions of this book. The radar astronomy experiments of the 
1940s and 1950s, as well as much of pre-war radar development, were intimately linked to 
ionospheric research, which was then undergoing a rapid publication rate typical of Big 
Science. 

Also, the evolutions of planetary radar and radio astronomy converged. The search for 
research instruments free of military constraints brought planetary radar astronomers 
closer to radio astronomy during the 1960s, a time when radio astronomy was undergoing 
a rapid growth that transformed it into Big Science. Planetary radar and radio astronomy 
shared instruments and a common interest in electronic hardware and techniques, 
though ironically the instrumentation needs of the two communities ultimately provided 
little basis for cohabitation. 

In the end, military Big Science was far more important than either radio astronomy or 
ionospheric science. Planetary radar astronomy emerged in the late 1950s thanks to Cold 
War defense research that furnished the essential instruments of planetary radar experi- 
mentation. The vulnerability of the United States to aircraft and ICBM attacks with 
nuclear explosives necessitated the creation of a network of ever more powerful and 
sensitive defensive radars. What President Dwight D. Eisenhower called the military- 
industrial complex, and what historian Stuart Leslie calls the military-industrial-academic 
complex, 1 provided the radar instrument for the first attempts at Venus. The military- 
industrial or military-industrial-academic complex served as the social matrix which nur- 
tured military and other Big Science research. Planetary radar astronomy eventually 
found itself part of a different, though at times interlocking, complex centered on the 
civilian enterprise to explore space, that is, what one might call the NASA-industrial- 
academic complex. 



1. Stuart W. Leslie, The Cold War and American Science: The Mititary-Industrial-Academic Complex at MIT 
and Stanford (New York: Columbia University Press, 1993). 



Vlll 



The emergence of space as Big Science under the financial and institutional aegis of 
NASA, and the design and construction of a worldwide network of antennas to track 
launches and communicate with spacecraft, furnished instruments for planetary radar 
research as early as 1961. Within a decade, NASA became the de facto underwriter of all 
planetary radar astronomy. Data on the nature of planetary surface features and precise 
reckoning of both the astronomical unit and planetary orbits were highly valuable to an 
institution whose primary goal was (and whose budgetary bulk paid for) the designing, 
building, and launching of vessels for the exploration of the solar system. Association with 
NASA Big Science enhanced the tendency of radar astronomers to emphasize the utility 
of their research and promoted mission-oriented, as opposed to basic, research. 

The history of planetary radar astronomy is intrinsically interesting and forms the frame- 
work of this book. It also says something about Big Science. Defining Big Science, or even 
Little Science, is not easy though. After all, how true are the images of the Little Scientist 
as "the lone, long-haired genius, moldering in an attic or basement workshop, despised by 
society as a nonconformist, existing in a state of near poverty, motivated by the flame 
burning within him," and the Big Scientist as "honored in Washington, sought after by all 
the research corporations of the 'Boston ring road,' part of an elite intellectual brother- 
hood of co-workers, arbiters of political as well as technological destiny"? 2 

Since the publication in 1963 of Derek J. De Solla Price's ground-breaking Little Science, 
Big Science, historians have attempted to define Big Science. 3 Their considerable efforts 
have clarified the meaning of the term, though without producing a universally authori- 
tative definition. If large-scale expensive research instruments are the measure, then one 
might count the island observatory of Tycho Brahe in the sixteenth century, or the giant 
electrical machines built in eighteenth-century Holland. If Big Science is a large grouping 
of investigators from several disciplines working together on a common project, then the 
gathering of mathematicians, chemists, and physicists at Thomas Edison's West Orange 
laboratory was Big Science. A long-term research project, such as the quest for an AIDS 
cure, or one that entails elaborate organization, such as the Manhattan Project, might be 
termed Big Science too. 

Defining Big Science is the intellectual equivalent of trying to nail Jell-O to the wall. For 
the purposes of this book, we shall call Big Science the large-scale organization of science 
and scientists, underwritten by an imposing pledge of (usually) public funds and centered 
around a complex scientific instrument. In his search to understand Big Science, Derek 
Price decided to "turn the tools of science on itself," charting the historical growth of sci- 
ence by means of a variety of statistical indicators obtained from the Institute for Scientific 
Information in Philadelphia. Price concluded that scientific activity (as measured by the 
amount of literature published) has grown exponentially over the last three hundred 
years, doubling in size about every fifteen years. 4 We also shall define a rapid growth in 
scientific literature greater than the Price rate (doubling every fifteen years) as indicating 



2. Derek J. DeSolla Price, Little Science, Big Science... and Beyond (New York: Columbia University Press, 
1986), p. 2. 

3. Price, Little Science, Big Science... and Beyond, p. 15.- 

4. Price, Little Science, Big Science (New York: Columbia University Press, 1963). This discussion of Big 
Science draws on Peter Galison and Bruce Hevly, eds., Big Science: The Growth of Large-Scale Research (Stanford: 
Stanford University Press, 1992); James H. Capshaw and Karen A. Rader, "Big Science: Price to the Present," 
Osiris, ser. 2, vol. 7 (1992): 3-25; and Joel Genuth, "Microwave Radar, the Atomic Bomb, and the Background to 
U.S. Research Priorities in World War II," Science, Technology, and Human Values 13 (1988): 276-289. 



an emerging Big Science field. Whatever it is, Big Science has become the dominant form 
of contemporary American science. Moreover, because of its scale and scope, the conduct 
of Big Science necessarily intrudes into many areas of society, and in turn, society, through 
political, economic, and other activity, shapes the conduct of Big Science. 

The interdependency of institutional factors, funding patterns, science, technology, and 
techniques found in Big Science has been the subject of extensive study by historians and 
sociologists of science and technology. Scholars traditionally have concerned themselves 
with both science and technology and their interactions. Such studies came to be termed 
"internalist," meaning that they dealt solely with the inner workings of science and tech- 
nology. In contrast stood the so-called "externalist" approaches, which emphasized the 
social, economic, political, and other factors neglected by the "internalists." 

Starting around 1980, sociologists of science, such as Michel Gallon, developed new 
approaches, which were introduced into the history of technology by Thomas P. Hughes. 
These new approaches came to be called generically the "social construction of technol- 
ogy." The "technosocial networks" of Gallon and the "systems" of Hughes consider the 
"internalist" and "externalist" aspects of technology as constituting a single continuum or 
"seamless web". Inventors, scientists, instruments, financing, institutions, politics, laws, 
and so forth are all equally part of the "technosocial network" or "system". 5 

The chief advantage of replacing the "internalist" and "externalist" dualism with the uni- 
tarian approach of the social construction school is the more sophisticated and certainly 
more complex view of the scientific, technical, economic, political, institutional, legal, and 
other aspects of Big Science that it offers. Moreover, by stressing that all components of a 
technosocial network are equal and necessary, the social construction approach dissuades 
us from emphasizing any one factor, "internal" or "external", over all others. 

The social construction approach is useful for creating a taxonomy of the factors that 
shape Big Science. Nonetheless, although they served as a guiding principle in the writ- 
ing of this book, social construction case studies do not go far enough; they fail to address 
the question that is, after chronicling the achievements of radar astronomy, central to this 
book namely the conduct of Little Science in the context of Big Science. Furthermore, 
in all the discussions of Big Science, with few exceptions, the symbiotic relationship 
between Big Science and Little Science has been overlooked. This relationship is 
especially relevant to the organization of science within NASA space missions. The scien- 
tists who conduct experiments from those spacecraft typify Little Science: they work 
individually or in small collaborative groups, often with graduate assistants, and have 
relatively small budgets and limited laboratory equipment. Participation in NASA space- 
craft missions induces these Little Scientists to function as part of a Big Science endeavor. 
The scientists are organized into both working groups around a single scientific 
instrument and disciplinary groups. They participate in the design of experiments and in 



5. For a discussion of this evolution, see John M. Staudenmaier, "Recent Trends in the History of 
Technology," The American Historical Review 95 (1990): 715-725, as well as Hughes, The Seamless Web: 
Technology, Science, Etcetera, Etcetera," Social Studies of Science 16 (1986): 281-292. The primary social con- 
struction works are Wiebe E. Bijker, Hughes, and Trevor Pinch, eds., The Social Construction of Technological 
Systems: New Directions in the Sociology and History of Technology (Cambridge: MIT Press, 1987), and Bijker and John 
Law, eds., Shaping Technology/Building Society: Studies in Sociotechnical Change (Cambridge: MIT Press, 1992). 



the decisions to drop or modify certain experiments, as well as in the design of the instru- 
ments themselves. The overall scale of operation and budget is beyond that normally 
encountered by Little Scientists. 

One noteworthy exception to the lack of literature dealing with the relationship between 
Big Science and Little Science is historian John Krige's study of British nuclear physics 
research in the period immediately following World War II. The Labor Government of 
Clement Attlee set out to equip the universities of Birmingham, Glasgow, Liverpool, 
Cambridge, and Oxford with particle accelerators for conducting high-energy nuclear 
physics research. The accelerator program involved the kinds of large-scale budgets and 
instruments that typify Big Science; however, research was conducted in a manner more 
typical of Little Science. Large multidisciplinary teams, in which physicists and engineers 
rubbed shoulders, did not form; rather the physicists remained individual academic 
researchers. 6 

Krige's case of "Big Equipment but not Big Science" finds its parallel in planetary radar 
astronomy. Big Science was the sine qua non of planetary radar astronomy, but planetary 
radar astronomy was not Big Science. It was, and remains, Little Science in terms of 
manpower, instruments, budget, and publications. Planetary radar astronomy took root 
within the interstices of Big Science, but rather than expand over time, it actually shrank. 

The field attained its largest size, in terms of personnel, instruments, and publications, 
during the 1960s. Although one can count five active instruments between 1961 and 1964, 
the greatest number to ever carry out planetary radar experiments, only three subse- 
quently sustained active research programs. That number fell to two instruments after 
1975. For much of the period between 1978 and 1986, only one instrument, indeed the 
only instrument to have an established and secure planetary radar astronomy research 
program, the Arecibo Observatory, was steadily active. 

The number of active planetary radar astronomers has declined since the 1960s too. As a 
group, they tend not to reproduce as easily or as abundantly as other scientists, and many 
practitioners in the long run find something else to do. Two paths artifacts of the field's 
evolution lead to a career in planetary radar astronomy. Many follow the traditional 
university path doctoral research on a planetary radar topic, followed by a research 
position that permits them to perform planetary radar experiments. Of the current prac- 
titioners, the most recent Ph.D. was granted in 1994, the second most recent in 1978. The 
path more followed: practitioners were hired to conduct planetary radar experiments. 

The declining instrument and manpower numbers are reflected in the planetary radar 
astronomy publication record (see Appendix: Planetary Radar Astronomy Publications) . 
Price has shown that science publications have doubled about every fifteen years over the 
last three centuries. The planetary radar publication curve differs markedly from that nor- 
mal growth pattern, suggesting a ceiling condition that has limited growth. The nature of 
that ceiling condition, as well as the causal factors for the declining size of the planetary 
radar enterprise, are part of the story of how planetary radar Little Science has been con- 
ducted within the framework of American Big Science. The association of planetary radar 



6. John Krige, The Installation of High-Energy Accelerators in Britain after the War: Big Equipment 
but not 'Big Science,'" in Michelangelo De Maria, Mario Grilli, and Fabio Sebastiani, eds., The Restructuring of 
Physical Sciences in Europe and the United States, 1945-1960 (Teaneck, NJ: World Scientific, 1989), pp. 488-501. 



Xi 



Little Science with NASA Big Science ultimately affected the conduct of planetary radar 
astronomy. Radar astronomers always had argued the utility of their efforts for space 
research; NASA mission-oriented support of planetary radar astronomy only reinforced 
that utilitarian inclination. As the story unfolds, other factors that shaped and amplified 
the utilitarian tendency of radar astronomers will rise to the surface. 

Its relationship with NASA Big Science also transformed planetary radar astronomy from 
an exclusively ground-based scientific activity to one that was conducted in space as well. 
During the 1960s, planetary radar astronomers distinguished their ground-based research 
from that conducted from spacecraft, which they characterized as space exploration as 
opposed to astronomy. Starting in the following decade, when NASA became its sole 
underwriter, planetary radar astronomy began to engage the planetary geology commu- 
nity largely through its ability to image and otherwise characterize planetary surfaces. 
NASA funded specific radar imaging projects. At the same time, NASA began planning 
two missions to Venus, Pioneer Venus and Magellan, in order to capture in radar images 
the features of that planet's surface. Its opaque atmosphere keeps Venus's surface hidden 
from sight and bars exploration with optical methods. 

Pioneer Venus and Magellan ultimately had a profound impact on the practice of plane- 
tary radar astronomy. In addition to enlarging the community of scientists using radar 
imagery and other data to encompass both geologists and astronomers, those two NASA 
missions erased the turf boundary between space exploration and ground-based plane- 
tary radar astronomy. Although Magellan in particular also gave radar astronomers a taste 
of Big Science, planetary radar astronomy did not permanently shift from Little to Big 
Science. Radar imaging from a spacecraft had limited prospects. Ultimately, the greatest 
consequence of Magellan for planetary radar astronomy was that it effectively ended 
ground-based radar observations of Venus, the chief object of radar research. 

The plan of this book is to relate the history of planetary radar astronomy from its origins 
in radar to the present day and secondarily to bring to light that history as a case of "Big 
Equipment but not Big Science". Chapter One sketches the emergence of radar astrono- 
my as an ongoing scientific activity at Jodrell Bank, where radar research revealed that 
meteors were part of the solar system. The chief Big Science driving early radar astrono- 
my experiments was ionospheric research. Chapter Two links the Cold War and the Space 
Race to the first radar experiments attempted on planetary targets, while recounting the 
initial achievements of planetary radar, namely, the refinement of the astronomical unit 
and the rotational rate and direction of Venus. 

Chapter Three discusses early attempts to organize radar astronomy and the efforts at 
MIT's Lincoln Laboratory, in conjunction with Harvard radio astronomers, to acquire 
antenna time unfettered by military priorities. Here, the chief Big Science influencing the 
development of planetary radar astronomy was radio astronomy. Chapter Four spotlights 
the evolution of planetary radar astronomy at the Jet Propulsion Laboratory, a NASA 
facility, at Cornell University's Arecibo Observatory, and at Jodrell Bank. A congeries of 
funding from the military, the National Science Foundation, and finally NASA marked 
that evolution, which culminated in planetary radar astronomy finding a single Big 
Science patron, NASA. 

Chapter Five analyzes planetary radar astronomy as a science using the theoretical frame- 
work provided by philosopher of science Thomas Kuhn. Chapter Six explores the shift in 



xii 



planetary radar astronomy beginning in the 1970s that resulted from its financial and 
institutional relationship with NASA Big Science. This shift saw the field 1) transform 
from an exclusively ground-based scientific activity to one conducted in space, as well as 
on Earth, and 2) capture the interest of planetary scientists from both the astronomy and 
geology communities. Chapter Seven relates how the Magellan mission was the culmina- 
tion of this evolution. Chapters Eight and Nine discuss the research carried out at ground- 
based facilities by this transformed planetary radar astronomy, as well as the upgrading of 
the Arecibo and Goldstone radars. 

The conclusion serves a dual purpose. It responds to the concern for the future of plan- 
etary radar astronomy expressed by many of the practitioners interviewed for this book, 
as well as to the author's wish to provide a slice of applied history that might be of value 
to both radar astronomers and policy makers. The conclusipn also appraises planetary 
radar as a case of "Big Equipment but not Big Science". It considers the factors that have 
limited the size of planetary radar, its utilitarian nature, and its dependency on large-scale 
technological enterprises. 

A technical essay appended to this book provides an overview of planetary radar tech- 
niques, especially range-Doppler mapping, for the general reader. Furthermore, the text 
itself explains certain, though not all, technical aspects of radar astronomy. The author 
assumed that the reader would have a familiarity with general technical and scientific ter- 
minology or would have access to a scientific dictionary or encyclopedia. For those read- 
ers seeking additional, and especially more technically-oriented, information on plane- 
tary radar astronomy, the technical essay includes a list of articles on the topic written by 
radar practitioners. 



Chapter One 

A Meteoric Start 



During the 1940s, investigators in the United States and Hungary bounced radar 
waves off the Moon for the first time, while others made the first systematic radar studies 
of meteors. These experiments constituted the initial exploration of the solar system with 
radar. In order to understand the beginnings of radar astronomy, we first must examine 
the origins of radar in radio, the decisive role of ionospheric research, and the rapid 
development of radar technology triggered by World War II. 

As early as 20 June 1922, in an address to a joint meeting of the Institute of Electrical 
Engineers and the Institute of Radio Engineers in New York, the radio pioneer Guglielmo 
Marconi suggested using radio waves to detect ships: 1 

As was first shown by Hertz, electric waves can be completely reflected by conduct- 
ing bodies. In some of my tests I have noticed the effects of reflection and deflection of these 
waves by metallic objects miles away. 

It seems to me that it should be possible to design apparatus by means of which a ship 
could radiate or project a divergent beam of these rays in any desired direction, which rays, 
if coming across a metallic object, such as another steamer or ship, would be reflected back 
to a receiver screened from the local transmitter on the sending ship, and thereby immedi- 
ately reveal the presence and bearing of the other ship in fog or thick weather. 

One further advantage of such an arrangement would be it would have the ability 
to give warning of the presence and bearing of ships, even should these ships be unpro- 
vided with any kind of radio. 

By the time Germany invaded Poland in September 1939 and World War II was 
underway, radio detection, location, and ranging technologies and techniques were avail- 
able in Japan, France, Italy, Germany, England, Hungary, Russia, Holland, Canada, and 
the United States. Radar was not so much an invention, springing from the laboratory 
bench to the factory floor, but an ongoing adaptation and refinement of radio technolo- 
gy. The apparent emergence of radar in Japan, Europe, and North America more or less 
at the same time was less a case of simultaneous invention than a consequence of the glob- 
al nature of radio research. 2 

Although radar is identified overwhelmingly with World War II, historian Sean S. 
Swords has argued that the rise of high-performance and long-range aircraft in the late 
1930s would have promoted the design of advanced radio navigational aids, including 
radar, even without a war. 3 More decisively, however, ionospheric research propelled radar 
development in the 1920s and 1930s. As historian Henry Guerlac has pointed out, "Radar 
was developed by men who were familiar with the ionospheric work. It was a relatively 
straightforward adaptation for military purposes of a widely-known scientific technique, 



1. Guglielmo Marconi, "Radio Telegraphy," Proceedings of the Institute of Radio Engineers 10 (1922): 237. 

2. Charles Susskind, "Who Invented Radar?" Endeavour^ (1985) : 92-96; Henry E. Guerlac, The Radio 
Background of Radar, " Journal of the Franklin Institute 250 (1950): 284-308. 

3. Swords, A Technical History of the Beginnings of Radar (London: Peter Peregrinus Press, 1986), 
pp. 270-271. 



TO SEE THE UNSEEN 



which explains why this adaptation the development of radar took place simultane- 
ously in several different countries." 4 

The prominence of ionospheric research in the history of radar and later of radar 
astronomy cannot be ignored. Out of ionospheric research came the essential technology 
for the beginnings of military radar in Britain, as well as its first radar researchers and 
research institutions. After the war, as we shall see, ionospheric research also drove the 
emergence of radar astronomy. 

Chain Home 

Despite its scientific origins, radar made its mark and was baptized during World War 
II as an integral and necessary instrument of offensive and defensive warfare. Located on 
land, at sea, and in the air, radars detected enemy targets and determined their position 
and range for artillery and aircraft in direct enemy encounters on the battlefield. Other 
radars identified aircraft to ground bases as friend or foe, while others provided naviga- 
tional assistance and coastal defense. World War II was the first electronic war, and radar 
was its prime agent. 5 

In 1940, nowhere did radar research achieve the same advanced state as in Britain. The 
British lead initially resulted from a decision to design and build a radar system for coastal 
defense, while subsequent research led to the invention of the cavity magnetron, which 
placed Britain in the forefront of microwave radar. The impetus to achieve that lead in radar 
came from a realization that the island nation was no longer safe from enemy invasion. 

For centuries, Britain's insularity and navy protected it from invasion. The advent of 
long-range airplanes that routinely outperformed their wooden predecessors spelled the 
end of that protection. Existing aircraft warning methods were ineffectual. That Britain 
was virtually defenseless against an air assault became clear during the summer air exer- 
cises of 1934. In simulated night attacks on London and Coventry, both the Air Ministry 
and the Houses of Parliament were successfully "destroyed," while few "enemy" bombers 
were intercepted. 6 

International politics also had reached a critical point. The Geneva Disarmament 
Conference had collapsed, and Germany was rearming in defiance of the Treaty of 
Versailles. Under attack from Winston Churchill and the Tory opposition, the British gov- 
ernment abandoned its disarmament policy and initiated a five-year expansion of the 
Royal Air Force. Simultaneously, the Air Ministry Director of Scientific Research, Henry 
Egerton Wimperis, created a committee to study air defense methods. 

Just before the Committee for the Scientific Survey of Air Defence first met on 28 
January 1935, Wimperis contacted fellow Radio Research Board member Robert (later 
Sir) Watson-Watt. Watson-Watt, who oversaw the Radio Research Station at Slough, was a 
scientist with twenty years of experience as a government researcher. Ionospheric research 
had been a principal component of Radio Research Station studies, and Watson-Watt fos- 
tered the development there of a pulse-height technique. 7 



4. Guerlac, "Radio Background," p. 304. 

5. Alfred Price, Instruments of Darkness: The History of Electronic Warfare, 2d. ed. (London: MacDonald 
and Jane's, 1977); Tony Devereux, Messenger Gods of Battle, Radio, Radar, Sonar: The Story of Electronics in War 
(Washington: Brassey's, 1991); David E. Fisher, A Race on the Edge of Time: Radar the Decisive Weapon of World War 
II (New York: McGraw-Hill, 1988). 

6. H. Montgomery Hyde, British Air Policy Between the Wars, 1918-1939 (London: Heinemann, 1976), 
p. 322. See also Malcolm Smith, British Air Strategy Between the Wan (Oxford, Clarendon Press, 1984). 

7. Swords, p. 84; Edward G. Bowen, Radar Days (Bristol: Adam Hilger, 1987), pp. 4-5, 7 and 10; Robert 
Watson-Watt, The Pulse of Radar: The Autobiography of Sir Robert Watson-Watt (New York: Dial Press, 1959), 
pp. 29-38, 51, 69, 101, 109-110, 113; A.P. Rowe, One Story of Radar (Cambridge: Cambridge University Press, 
1948), pp. 6-7; Reg Batt, The Radar Army: Winning the War of the Airwaves (London: Robert Hale, 1991), 
pp. 21-22. The Radio Research Board was under the Department of Scientific and Industrial Research, created 
in 1916. 



A METEORIC START 



The pulse-height technique was to send short pulses of radio energy toward the 
ionosphere and to measure the time taken for them to return to Earth. The elapsed trav- 
el time of the radio waves gave the apparent height of the ionosphere. Merle A. Tuve, then 
of Johns Hopkins University, and Gregory Breit of the Carnegie Institution's Department 
of Terrestrial Magnetism in Washington, first developed the technique in the 1920s and 
undertook ionospheric research in collaboration with the Naval Research Laboratory and 
the Radio Corporation of America. 8 

In response to the wartime situation, Wimperis asked Watson-Watt to determine the 
practicality of using radio waves as a "death ray." Rather than address the proposed "death 
ray," Watson-Watt's memorandum reply drew upon his experience in ionospheric 
research. Years later, Watson-Watt contended, "I regard this Memorandum on the 
'Detection and Location of Aircraft by Radio Methods' as marking the birth of radar and 
as being in fact the invention of radar." 9 Biographer Ronald William Clark has termed the 
memorandum "the political birth of radar." Nonetheless, Watson-Watt's memorandum 
was really less an invention than a proposal for a new radar application. 

The memorandum outlined how a radar system could be put together and made to 
detect and locate enemy aircraft. The model for that radar system was the same pulse- 
height technique Watson-Watt had used at Slough. Prior to the memorandum in its final 
form going before the Committee, Wimperis had arranged for a test of Watson-Watt's idea 
that airplanes could reflect significant amounts of radio energy, using a BBC transmitter 
at Daventry. "Thus was the constricting 'red tape' of official niceties slashed by Harry 
Wimperis, before the Committee for the Scientific Survey of Air Defence had so much as 
met," Watson-Watt later recounted. The success of the Daventry test shortly led to the 
authorization of funding (12,300 for the first year) and the creation of a small research 
and development project at Orford Ness and Bawdsey Manor that drew upon the exper- 
tise of the Slough Radio Research Station. 

From then onwards, guided largely by Robert Watson-Watt, the foundation of the 
British radar effort, the early warning Chain Home, materialized. The Chain Home began 
in December 1935, with Treasury approval for a set of five stations to patrol the air 
approaches to the Thames estuary. Before the end of 1936, and long before the first test 
of the Thames stations in the autumn of 1937, plans were made to expand it into a 
network of nineteen stations along the entire east coast; later, an additional six stations 
were built to cover the south coast. 



Born Robert Alexander Watson Watt in 1892, he changed his surname to "Watson-Watt" when knighted 
in 1942. See the popularly-written biography of Watson-Watt, John Rowland, The Radar Man: The Story of Sir Robert 
Watson-Watt (London: Lutterworth Press, 1963), or Watson-Watt, Three Steps to Victory (London: Odhams Press 
Ltd., 1957). An account of Watson-Watt's research at Slough is given in Watson-Watt, John F. Herd, and L.H. 
Bainbridge-Bell, The Cathode Ray Tube in Radio Research (London: His Majesty's Stationery Office, 1933). 

8. By "apparent height of the ionosphere," I mean what ionosphericists call virtual height. Since the 
ionosphere slows radio waves before being refracted back to Earth, the delay is not a true measure of height. 
The Tuve-Breit method preceded that of Watson-Watt and was a true send-receive technique, while that of 
Watson-Watt was a receive-only technique. 

Tuve "Early Days of Pulse Radio at the Carnegie Institution, " Journal of Atmospheric and Terrestrial Physics 36 
(1974): 2079-2083; Oswald G. Villard, Jr., "The Ionospheric Sounder and its Place in the History of Radio 
Science," Radio Science 11 (1976): 847-860; Guerlac, "Radio Background," pp. 284-308; David H. DeVorkin, 
Science With a Vengeance: How the Military Created the U.S. Space Sciences after World War II (New York: Springer-Verlag, 
1992), pp. 12, 301 and 316; C. Stewart Gillmor, Threshold to Space: Early Studies of the Ionosphere," in Paul 
A. Hanle and Von Del Chamberlin, eds., Space Science Comes of Age: Perspectives in the History of the Space Sciences 
(Washington: National Air and Space Museum, Smithsonian Institution, 1981), pp. 102-104; JA. Ratcliffe, 
"Experimental Methods of Ionospheric Investigation, 1925-1955," Journal of Atmospheric and Terrestrial Physics 36 
(1974): 2095-2103; Tuve and Breit, "Note on a Radio Method of Estimating the Height of the Conducting 
Layer," Terrestrial Magnetism and Atmospheric Electricity 30 (1925): 15-16; Breit and Tuve, "A Radio Method of 
Estimating the Height of the Conducting Layer," Nature 116 (1925): 357; and Breit and Tuve, "A Test of the 
Existence of the Conducting Layer," Physical Review 2d ser., vol. 28 (1926): 554-575; special issue of Journal of 
Atmospheric and Terrestrial Physics 36 (1974): 2069-2319, is devoted to the history of ionospheric research. 

9. Watson-Watt, Three Steps, p. 83; Ronald William Clark, Tizard (London: Methuen, 1965), pp. 105-127. 



TO SEE THE UNSEEN 



The Chain Home played a crucial role in the Battle of Britain, which began in July 
1940. The final turning point was on 15 September, when the Luftwaffe suffered a record 
number of planes lost in a single day. Never again did Germany attempt a massive daylight 
raid over Britain. However, if radar won the day, it lost the night. Nighttime air raids 
showed a desperate need for radar improvements. 



The Magnetron 



In order to wage combat at night, fighters needed the equivalent of night vision 
their own on-board radar, but the prevailing technology was inadequate. Radars operating 
at low wavelengths, around 1 .5 meters (200 MHz) , cast a beam that radiated both straight 
ahead and downwards. The radio energy reflected from the Earth was so much greater 
than that of the enemy aircraft echoes that the echoes were lost at distances greater than 
the altitude of the aircraft. At low altitudes, such as those used in bombing raids or in air- 
to-air combat, the lack of radar vision was grave. Microwave radars, operating at wave- 
lengths of a few centimeters, could cast a narrower beam and provide enough resolution 
to locate enemy aircraft. 10 

Although several countries had been ahead of Britain in microwave radar technolo- 
gy before the war began, Britain leaped ahead in February 1940, with the invention of the 
cavity magnetron by Henry A. H. Boot and John T. Randall at the University of 
Birmingham. 11 Klystrons were large vacuum tubes used to generate microwave power, but 
they did not operate adequately at microwave frequencies. The time required for elec- 
trons to flow through a klystron was too long to keep up with the frequency of the exter- 
nal oscillating circuit. The cavity magnetron resolved that problem and made possible the 
microwave radars of World War II. As Sean Swords asserted, 'The emergence of the 
resonant-cavity magnetron was a turning point in radar history." 12 The cavity magnetron 
launched a line of microwave research and development that has persisted to this day. 

The cavity magnetron had no technological equivalent in the United States, when 
the Tizard Mission arrived in late 1940 with one of the first ten magnetrons constructed. 
The Tizard Mission, known formally as the British Technical and Scientific Mission, had 
been arranged at the highest levels of government to exchange technical information 
between Britain and the United States. Its head and organizer, Henry Tizard, was a promi- 
nent physics professor and a former member of the committee that had approved Watson- 
Watt's radar project. As James P. Baxter wrote just after the war's end with a heavy hand- 
ful of hyperbole, though not without some truth: "When the members of the Tizard 
Mission brought one [magnetron] to America in 1940, they carried the most valuable 
cargo ever brought to our shores. It sparked the whole development of microwave radar 
and constituted the most important item in reverse Lease-Lend." 13 



10. Swords, pp. 84-85; Bowen, pp. 6, 21, 26 and 28; Batt, pp. 10, 21-22, 69 and 77; Rowe, pp. 8 and 76; 
R. Hanbury Brown, Boffin: A Personal Story of the Early Days of Radar, Radio Astronomy, and Quantum Optics (Bristol: 
Adam Hilger, 1991), pp. 7-8; P.S. Hall and R.G. Lee, "Introduction to Radar," in P.S. Hall, T.K. Garland-Collins, 
R.S. Picton, and R.G. Lee, eds., Radar (London: Brassey's, 1991), pp. 6-7; Watson-Watt, Pulse, pp. 55-59, 64-65, 
75, 1 13-1 15 and 427-434; Watson-Watt, Three Steps, pp. 83 and 470-474; Bowen, The Development of Airborne 
Radar in Great Britain, 1935-1945," in Russel W. Burns, ed., Radar Development to 1945 (London: Peter 
Peregrinus Press, 1988), pp. 177-188. For a description of the technology, see B.T. Neale, "CH the First 
Operational Radar," in Burns, pp. 132-150. 

11. Boot and Randall, "Historical Notes on the Cavity Magnetron," IEEE Transactions on Electron Devices 
ED-23 (1976): 724-729; R.W. Burns, "The Background to the Development of the Cavity Magnetron," in Burns, 
pp. 259-283. 

12. Swords, p. xi. 

13. Baxter, Scientists Against Time (Boston: Little, Brown and Company, 1946), p. 142; Swords, pp. 120, 
259, and 266; Clark, especially pp. 248-271. 



A METEORIC START 



In late September 1940, Dr. Edward G. Bowen, the radar scientist on the Tizard 
Mission, showed a magnetron to members of the National Defense Research Committee 
(NDRC), which President Roosevelt had just created on 27 June 1940. One of the first acts 
of the NDRC, which later became the Office of Scientific Research and Development, was 
to establish a Microwave Committee, whose stated purpose was "to organize and consoli- 
date research, invention, and development as to obtain the most effective military 
application of microwaves in the minimum time." 14 

A few weeks after the magnetron demonstration, the NDRC decided to create the 
Radiation Laboratory at MIT. While the MIT Radiation Laboratory accounted for nearly 
80 percent of the NDRC Microwave Division's contracts, an additional 136 contracts for 
radar research, development, and prototype work were let out to sixteen colleges and 
universities, two private research institutions, and the major radio industrial concerns, 
with Western Electric taking the largest share. The MIT Radiation Laboratory personnel 
skyrocketed from thirty physicists, three guards, two stock clerks, and a secretary for the 
first year to a peak employment level of 3,897 (1,189 of whom were staff) on 1 August 
1945. The most far-reaching early achievement, accomplished in the spring of 1941, was 
the creation of a new generation of radar equipment based on a magnetron operating at 
3 cm. Experimental work in the one cm range led to numerous improvements in radars 
at 10 and 3 cm. 15 

Meanwhile, research and development of radars of longer wavelengths were carried 
out by the Navy and the Army Signal Corps, both of which had had active ongoing radar 
programs since the 1930s. The Navy started its research program at the Naval Research 
Laboratory (NRL) before that of the Signal Corps, but radar experimenters after the war 
used Signal Corps equipment, especially the SCR-270, mainly because of its wide avail- 
ability. A mobile SCR-270, placed on Oahu as part of the Army's Aircraft Warning System, 
spotted incoming Japanese airplanes nearly 50 minutes before they bombed United States 
installations at Pearl Harbor on 7 December 1941. The warning was ignored, because an 
officer mistook the radar echoes for an expected flight of B-l7s. 16 

Historians view the large-scale collection of technical and financial resources and 
manpower at the MIT Radiation Laboratory engaged in a concerted effort to research 
and develop new radar components and systems, along with the Manhattan Project, as 



14. Guerlac, Radar in World War II, The History of Modern Physics, 1800-1950, vol. 8 (New York: 
Tomash Publishers for the American Institute of Physics, 1987), vol. 1, p. 249; Swords, pp. 90 and 119; Batt, pp. 
79-80; Bowen, pp. 159-162: Watson Watt, Pulse, pp. 228-229 and 257; Watson-Watt, Three Steps, 293. 

In addition to Tizard and Bowen, the Mission team consisted of Prof. J.D. Cockcroft, Col. F.C. Wallace, 
Army, Capt. H.W. Faulkner, Navy, Capt. F.L. Pearce, Royal Air Force, WE. Woodward Nutt, Ministry of Aircraft 
Production, Mission Secretary, Prof. R.H. Fowler, liaison officer for Canada and the United States of the 
Department of Scientific and Industrial Research, and Col. H.F.G. Letson, Canadian military attache in 
Washington. 

15. Guerlac, Radar in World War II, 1:258-259, 261, 266 and 507-508, and 2:648 and 668. See also the 
personal reminiscences of Ernest C. Pollard, Radiation: One Story of the MIT Radiation Laboratory (Durham: The 
Woodburn Press, 1982). Interviews (though not all are transcribed) of some Radiation Laboratory participants 
are available at the IEEE Center for the History of Electrical Engineering (CHEE), Rutgers University. CHEE, 
Sources in Electrical History 2: Oral History Collections in U.S. Repositories (New York: IEEE, 1992) , pp. 6-7. The British 
also developed magnetrons and radar equipment operating at microwave frequencies concurrently with the MIT 
Radiation Laboratory effort. 

16. Guerlac, Radar in World War II, 1:247-248 and 117-119. For die Navy, see LA. Hyland, "A Personal 
Reminiscence: The Beginnings of Radar, 1930-1934," in Burns, pp. 29-33; Robert Morris Page, The Origin of 
Radar (Garden City, NY: Anchor Books, Doubleday & Company, 1962); Page, "Early History of Radar in die U.S. 
Navy," in Burns, pp. 35-44; David Kite Allison, New Eye for the Navy: The Origin of Radar at the Naval Research 
Laboratory (Washington: Naval Research Laboratory, 1981); Guerlac, Radar in World War II, 1:59-92; Albert Hoyt 
Taylor, The Pint Twenty-five Yean of the Naval Research Laboratory (Washington: Navy Department, 1948) . On die 
Signal Corps, see Guerlac, Radarin World War II, 1:93-121; Harry M. Davis, History of the Signal Corps Development 
of U.S. Army Radar Equipment (Washington: Historical Section Field Office, Office of the Chief Signal Officer, 
1945); Arthur L. Vieweger, "Radar in die Signal Corps," IRE Transactions on Military Electronics MIL-4 (1960): 
555-561. 



TO SEE THE UNSEEN 



signalling the emergence of Big Science. Ultimately, from out of the concentration of 
personnel, expertise, materiel, and financial resources at the successor of the Radiation 
Laboratory, Lincoln Laboratory, arose the first attempts to detect the planet Venus with 
radar. The Radiation Laboratory Big Science venture, however, did not contribute imme- 
diately to the rise of radar astronomy. 

The radar and digital technology used in those attempts on Venus was not available 
at the end of World War II, when the first lunar and meteor radar experiments were 
conducted. Moreover, the microwave radars issued from Radiation Laboratory research 
were far too weak for planetary or lunar work and operated at frequencies too high to be 
useful in meteor studies. Outside the Radiation Laboratory, though, U.S. Army Signal 
Corps and Navy researchers had created radars, like the SCR-270, that were more power- 
ful and operated at lower frequencies, in research and development programs that were 
less concentrated and conducted on a smaller scale than the Radiation Laboratory effort. 

Wartime production created an incredible excess of such radar equipment. The end 
of fighting turned it into war surplus to be auctioned off, given away, or buried as waste. 
World War II also begot a large pool of scientists and engineers with radar expertise who 
sought peacetime scientific and technical careers at war's end. That pool of expertise, 
when combined with the cornucopia of high-power, low-frequency radar equipment and 
a pinch of curiosity, gave rise to radar astronomy. 

A catalyst crucial to that rise was ionospheric research. In the decade and a half 
following World War II, ionospheric research underwent the kind of swift growth that is 
typical of Big Science. The ionospheric journal literature doubled every 2.9 years from 
1926 to 1938, before stagnating during the war; but between 1947 and 1960, the literature 
doubled every 5.8 years, a rate several times faster than the growth rate of scientific liter- 
ature as a whole. 17 Interest in ionospheric phenomena, as expressed in the rapidly 
growing research literature, motivated many of the first radar astronomy experiments 
undertaken on targets beyond the Earth's atmosphere. 



Project Diana 



Typical was the first successful radar experiment aimed at the Moon. That experi- 
ment was performed with Signal Corps equipment at the Corps' Evans Signal Laboratory, 
near Belmar, New Jersey, under the direction of John H. DeWitt, Jr., Laboratory Director. 
DeWitt was born in Nashville and attended Vanderbilt University Engineering School for 
two years. Vanderbilt did not offer a program in electrical engineering, so DeWitt 
dropped out in order to satisfy his interest in broadcasting and amateur radio. In 1929, 
after building Nashville's first broadcasting station, DeWitt joined the Bell Telephone 
Laboratories technical staff in New York City, where he designed radio broadcasting trans- 
mitters. He returned to Nashville in 1932 to become Chief Engineer of radio station WSM. 
Intrigued by Karl Jansky's discovery of "cosmic noise," DeWitt built a radio telescope and 
searched for radio signals from the Milky Way. 

In 1940, DeWitt attempted to bounce radio signals off the Moon in order to study 
the Earth's atmosphere. He wrote in his notebook: "It occurred to me that it might be 
possible to reflect ultrashort waves from the moon. If this could be done it would open up 
wide possibilities for the study of the upper atmosphere. So far as I know no one has ever 



17. Gillmor, "Geospace and its Uses: The Restructuring of Ionospheric Physics Following World War II," 
in DeMaria, Grilli, and Sebastiani, pp. 75-84, especially pp. 78-79. 

18. DeWitt notebook, 21 May 1940, and DeWitt biographical sketch, HL Diana 46 (04), HAUSACEC. 
There is a rich literature on Jansky's discovery. A good place to start is Woodruff T. Sullivan III, "Karl Jansky and 
the Discovery of Extraterrestrial Radio Waves," in Sullivan, ed., The Early Years of Radio Astronomy: Reflections Fifty 
Years after Jansky's Discovery (New York: Cambridge University Press, 1984), pp. 3-42. 



A METEORIC START 



sent waves off the earth and measured their return through the entire atmosphere of the 
earth." 18 

On the night of 20 May 1940, using the receiver and 80-watt transmitter configured 
for radio station WSM, DeWitt tried to reflect 138-MHz (2-meter) radio waves off the 
Moon, but he failed because of insufficient receiver sensitivity. After joining the staff of 
Bell Telephone Laboratories in Whippany, New Jersey, in 1942, where he worked exclu- 
sively on the design of a radar antenna for the Navy, DeWitt was commissioned in the 
Signal Corps and was assigned to serve as Executive Officer, later as Director, of Evans 
Signal Laboratory. 

On 10 August 1945, the day after the United States unleashed a second atomic bomb 
on Japan, military hostilities between the two countries ceased. DeWitt was not demobi- 
lized immediately, and he began to plan his pet project, the reflection of radio waves off 
the Moon. He dubbed the scheme Project Diana after the Roman mythological goddess 
of the Moon, partly because "the Greek [sic] mythology books said that she had never 
been cracked." 

In September 1945, DeWitt assembled his team: Dr. Harold D. Webb, Herbert P. 
Kauffman, E. King Stodola, and Jack Mofenson. Dr. Walter S. McAfee, in the Laboratory's 
Theoretical Studies Group, calculated the reflectivity coefficient of the Moon. Members 
of the Antenna and Mechanical Design Group, Research Section, and other Laboratory 
groups contributed too. 

No attempt was made to design major components specifically for the experiment. 
The selection of the receiver, transmitter, and antenna was made from equipment already 
on hand, including a special crystal-controlled receiver and transmitter designed for the 
Signal Corps by radio pioneer Edwin H. Armstrong. Crystal control provided frequency 
stability, and the apparatus provided the power and bandwidth needed. The relative veloc- 
ities of the Earth and the Moon caused the return signal to differ from the transmitted 
signal by as much as 300 Hz, a phenomenon known as Doppler shift. The narrow-band 
receiver permitted tuning to the exact radio frequency of the returning echo. As DeWitt 
later recalled: "We realized that the moon echoes would be very weak so we had to use a 
very narrow receiver bandwidth to reduce thermal noise to tolerable levels. ...We had to 
tune the receiver each time for a slightly different frequency from that sent out because 
of the Doppler shift due to the earth's rotation and the radial velocity of the moon at the 
time." 19 

The echoes were received both visually, on a nine-inch cathode-ray tube, and acousti- 
cally, as a 180-Hz beep. The aerial was a pair of "bedspring" antennas from an SCR-271 sta- 
tionary radar positioned side by side to form a 32-dipole array antenna and mounted on 
a 30-meter (100-ft) tower. The antenna had only azimuth control; it had not been practi- 
cal to secure a better mechanism. Hence, experiments were limited to the rising and set- 
ting of the Moon. 



19. DeWitt to Trevor Clark, 18 December 1977, HL Diana 46 (04) ; "Background Information on DeWitt 
Observatory" and "U.S. Army Electronics Research and Development Laboratory, Fort Monmouth, New Jersey," 
March 1963, HL Diana 46 (26) , HAUSACEC. For published full descriptions of the equipment and experiments, 
see DeWitt and E. King Stodola, "Detection of Radio Signals Reflected from the Moon," Proceedings of the Institute 
of Radio Engineers 37 (1949): 229-242; Jack Mofenson, "Radar Echoes from the Moon," Electronics 19 (1946): 
92-98; and Herbert Kauffman, "A DX Record: To the Moon and Back," QST30 (1946): 65-68. 



TO SEE THE UNSEEN 




Figure 1 

The "bedspring" mast antenna, U.S. Army Signal Corps, Ft. Monmouth, New Jersey, used by Lt. Col. John H. DeWiU,Jr, to 
bounce radar echoes off the Moon on 10 January 1946. Two antennas from SCR-271 stationary radars were positioned side 
by side to form a 32-dipole array aerial and were mounted on a 100-fi (3frmeter) tower. (Courtesy of the U.S. Army 
Communications-Electronics Museum, Ft. Monmouth, New Jersey.) 



A METEORIC START 



The Signal Corps tried several times, but without success. 'The equipment was very 
haywire," recalled DeWitt. Finally, at moonrise, 11:48 A.M., on 10 January 1946, they 
aimed the antenna at the horizon and began transmitting. Ironically, DeWitt was not pre- 
sent: "I was over in Belmar having lunch and picking up some items like cigarettes at the 
drug store (stopped smoking 1952 thank God)." 20 The first signals were detected at 11:58 
A.M., and the experiment was concluded at 12:09 P.M., when the Moon moved out of the 
radar's range. The radio waves had taken about 2.5 seconds to travel from New Jersey to 
the Moon and back, a distance of over 800,000 km. The experiment was repeated daily 
over the next three days and on eight more days later that month. 

The War Department withheld announcement of the success until the night of 
24 January 1946. By then, a press release explained, "the Signal Corps was certain beyond 
doubt that the experiment was successful and that the results achieved were pain-staking- 
ly [sic] verified." 21 

As DeWitt recounted years later: "We had trouble with General Van Deusen our head 
of R&D in Washington. When my C.O. Col. Victor Conrad told him about it over the tele- 
phone the General did not want the story released until it was confirmed by outsiders for 
fear it would embarrass the Sigfnal]. C[orps]." Two outsiders from the Radiation 
Laboratory, George E. Valley, Jr. and Donald G. Fink, arrived and, with Gen. Van Deusen, 
observed a moonrise test of the system carried out under the direction of King Stodola. 
Nothing happened. DeWitt explained: "You can imagine that at this point I was dying. 
Shortly, a big truck passed by on the road next to the equipment and immediately the 
echoes popped up. I will always believe that one of the crystals was not oscillating until it 
was shaken up or there was a loose connection which fixed itself. Everyone cheered 
except the General who tried to look pleased." 22 

Although he had had other motives for undertaking Project Diana, DeWitt had 
received a directive from the Chief Signal Officer, the head of the Signal Corps, to devel- 
op radars capable of detecting missiles coming from the Soviet Union. No missiles were 
available for tests, so the Moon experiment stood in their place. Several years later, the 
Signal Corps erected a new 50-ft (15-meter) Diana antenna and 108-MHz transmitter for 
ionospheric research. It carried out further lunar echo studies and participated in the 
tracking of Apollo launches. 23 

The news also hit the popular press. The implications of the Signal Corps experi- 
ment were grasped by the War Department, although Newsweek cynically cast doubt on the 
War Department's predictions by calling them worthy of Jules Verne. Among those War 
Department predictions were the accurate topographical mapping of the Moon and plan- 
ets, measurement and analysis of the ionosphere, and radio control from Earth of "space 
ships" and 'jet or rocket-controlled missiles, circling the Earth above the stratosphere." 
Time reported that Diana might provide a test of Albert Einstein's Theory of Relativity. In 
contrast to the typically up-beat mood of Life, both news magazines were skeptical, and 



20. DeWitt replies to Clark questions, HL Diana 46 (04) , HAUSACEC. 

21 . HL Radar 46 (07) , HAUSACEC; Harold D. Webb, "Project Diana: Army Radar Contacts the Moon," 
Sky and Telescope 5 (1946): 3-6. 

22. DeWitt to Clark, 18 December 1977, HL Diana 46 (04), HAUSACEC; Guerlac, Radar in World War 
II, 1:380 and 382, 2:702. 

23. DeWitt, telephone conversation, 14 June 1993; Materials in folders HL Diana 46 (25), HL Diana 46 
(28), and HL Diana 46 (33), USASEL Research & Development Summary vol. 5, no. 3 (10 February 1958): 58, in 
"Signal Corps Engineering Laboratory Journal/R&D Summary," and Mimmouth Message, 7 November 1963, n.p., 
in "Biographical Files," "Daniels, Fred Bryan," HAUSACEC; Daniels, "Radar Determination of the Scattering 
Properties of the Moon," Nature 187 (1960): 399; and idem., "A Theory of Radar Reflection from the Moon and 
Planets," Journal of Geophysical Research 66 (1961): 1781-1788. 



1 TO SEE THE UNSEEN 



rightly so; yet all of the predictions made by the War Department, including the relativity 
test, have come true in the manner of a Jules Verne novel. 24 

Zoltan Bay 

Less than a month after DeWitt's initial experiment, a radar in Hungary replicated 
his results. The Hungarian apparatus differed from that of DeWitt in one key respect; it 
utilized a procedure, called integration, that was essential to the first attempt to bounce 
radar waves off Venus and that later became a standard planetary radar technique. The 
procedure's inventor was Hungarian physicist Zoltan Bay. 

Bay graduated with highest honors from Budapest University with a Ph.D. in physics 
in 1926. Like many Hungarian physicists before him, Bay spent several years in Berlin on 
scholarships, doing research at both the prestigious Physikalisch-Technische-Reichanstalt 
and the Physikalisch-Chemisches-Institut of the University of Berlin. The results of his 
research tour of Berlin earned Bay the Chair of Theoretical Physics at the University of 
Szeged (Hungary), where he taught and conducted research on high intensity gas dis- 
charges. 

Bay left the University of Szeged when the United Incandescent Lamps and Electric 
Company (Tungsram) invited him to head its industrial research laboratory in Budapest. 
Tungsram was the third largest manufacturer of incandescent lamps, radio tubes, and 
radio receivers in Europe and supplied a fifth of all radio tubes. As laboratory head, 
Zoltan Bay oversaw the improvement of high-intensity gas discharge lamps, fluorescent 
lamps, radio tubes, radio receiver circuitry, and decimeter radio wave techniques. 25 

Although Hungary sought to stay out of the war through diplomatic maneuvering, 
the threat of a German invasion remained real. In the fall of 1942, the Hungarian Minister 
of Defense asked Bay to organize an early-warning system. He achieved that goal, though 
the Germans occupied Hungary anyway. In March 1944, Bay recommended using the 
radar for scientific experimentation, including the detection of radar waves bounced off 
the Moon. The scientific interest in the experiment arose from the opportunity to test the 
theoretical notion that short wavelength radio waves could pass through the ionosphere 
without considerable absorption or reflection. Bay's calculations, however, showed that 
the equipment would be incapable of detecting the signals, since they would be signifi- 
cantly below the receiver's noise level. 

The critical difference between the American and Hungarian apparatus was fre- 
quency stability, which DeWitt achieved through crystal control in both the transmitter 
and receiver. Without frequency stability, Bay had to find a means of accommodating the 
frequency drifts of the transmitter and receiver and the resulting inferior signal-to-noise 
ratio. He chose to boost the signal-to-noise ratio. His solution was both ingenious and far- 
reaching in its impact. 

Bay devised a process he called cumulation, which is known today as integration. His 
integrating device consisted of ten coulometers, in which electric currents broke down a 
watery solution and released hydrogen gas. The amount of gas released was directly 
proportional to the quantity of electric current. The coulometers were connected to the 
output of the radar receiver through a rotating switch. The radar echoes were expected 



24. "Diana," Time Vol. 47, no. 5 (4 February 1946): 84; "Radar Bounces Echo off the Moon to Throw 
Light on Lunar Riddle," Newsweek vol. 27, no. 5 (4 February 1946): 76-77; "Man Reaches Moon with Radar," Life 
vol. 20, no. 5 (4 February 1946): 30. 

25. Zoltan Bay, Life is Stronger, trans. Margaret Blakey Hajdu (Budapest: Puski Publisher, 1991), pp. 5 
and 17-18; Francis S. Wagner, Zoltan Bay, Atomic Physicist: A Pioneer of Spaa Research (Budapest: Akademiai Kiado, 
1985), pp. 23-27, 29, 31-32; Wagner, Fifty Years in the Laboratory: A Survey of the Research Activities of Physicist Zoltan 
Bay (Center Square, PA: Alpha Publications, 1977), p. 1. 



A METEORIC START 



11 



to return from the Moon in less than three seconds, so the rotating switch made a sweep 
of the ten coulometers every three seconds. The release of hydrogen gas left a record of 
both the echo signal and the receiver noise. As the number of signal echoes and sweeps 
of the coulometers added up, the signal-to-noise ratio improved. By increasing the total 
number of signal echoes, Bay believed that any signal could be raised above noise level 
and made observable, regardless of its amplitude and the value of the signal-to-noise 
ratio. 26 Because the signal echoes have a more-or-less fixed structure, and the noise varies 
from pulse to pulse, echoes add up faster than noise. 

Despite the conceptual breakthrough of the coulometer integrator, the construction 
and testing of the apparatus remained to be carried out. The menace of air raids drove 
the Tungsram research laboratory into the countryside in the fall of 1944. The subsequent 
siege of Budapest twice interrupted the work of Bay and his team until March 1945. The 
Ministry of Defense furnished Bay with war surplus parts for a 2.5-meter (120-MHz) radar 

manufactured by the 
Standard Electrical Co., a 
Hungarian subsidiary of ITT. 
Work was again interrupted 
when the laboratory was dis- 
mantled and all equipment, 
including that for the lunar 
radar experiment, was carried 
off to the Soviet Union. For a 
third time, construction of 
entirely new equipment start- 
ed in the workshops of the 
Tungsram Research Laboratory, 
beginning August 1945 and 
ending January 1946. 

Electrical disturbances 
in the Tungsram plant were 
so great that measurements 
and tuning had to be done in 
the late afternoon or at night. 
The experiments were carried 
out on 6 February and 8 May 
1946 at night by a pair of 
researchers. Without the 
handicap of operating in a 
war zone, Bay probably would 
have beaten the Signal Corps 
to the Moon, although he 
could not have been aware of 
DeWitt's experiment. More 

Figure 2 . . l , , , 

Antenna built and used by Zoltdn Bay to bounce radar echoes off the Moon in mportantly, though, he 
February and May 1946. (Courtesy of Mrs. Julia Bay) invented the technique of 




26. Bay, "Reflection of Microwaves from the Moon," Hungarica Acta Physica 1 (1947): 1-6; Bay, Life is 
Stronger, pp. 20 & 29; Wagner, Zoltdn, pp. 39-40; Wagner, Fifty Years, pp. 1-2. 



1 2 TO SEE THE UNSEEN 



long-time integration generally used in radar astronomy. As the American radio 
astronomers Alex G. Smith and Thomas D. Carr wrote some years later: 'The additional 
tremendous increase in sensitivity necessary to obtain radar echoes from Venus has been 
attained largely through the use of long-time integration techniques for detecting peri- 
odic signals that are far below the background noise level. The unique method devised by 
Bay in his pioneer lunar radar investigations is an example of such a technique." 27 

Both Zoltan Bay and John DeWitt had fired shots heard round the world, but there 
was no revolution, although others either proposed or attempted lunar radar experiments 
in the years immediately following World War II. Each man engaged in other projects 
shortly after completing his experiment. Bay left Hungary for the United States, where he 
taught at George Washington University and worked for the National Bureau of 
Standards, while DeWitt re-entered radio broadcasting and pursued his interest in astron- 
omy. 28 

As an ongoing scientific activity, radar astronomy did not begin with the spectacular 
and singular experiments of DeWitt and Bay, but with an interest in meteors shared by 
researchers in Britain, Canada, and the United States. Big Science, that is, ionospheric 
physics and secure military communications, largely motivated that research. Moreover, 
just as the availability of captured V-2 parts made possible rocket-based ionospheric 
research after the war, 29 so war-surplus radars facilitated the emergence of radar astrono- 
my. Like the exploration of the ionosphere with rockets, radar astronomy was driven by 
the availability of technology. 

Meteors and Auroras 

Radar meteor studies, like much of radar history, grew out of ionospheric research. 
In the 1930s, ionospheric researchers became interested in meteors when it was hypothe- 
sized that the trail of electrons and ions left behind by falling meteors caused fluctuations 
in the density of the ionosphere. 30 Edward Appleton and others with the Radio Research 
Board of the British Department of Scientific and Industrial Research, the same organi- 
zation with which Watson-Watt had been associated, used war-surplus radar furnished by 



27. Smith and Carr, Radio Exploration of the Planetary System (New York: D. Van Nostrand, 1964) , p. 123; 
Bay, "Reflection," pp. 2, 7-15 and 18-19; P. Vajda andJA. White, Thirtieth Anniversary of Zoltan Bay's Pioneer 
Lunar Radar Investigations and Modern Radar Astronomy," Acta Physica Academiae Scientiarum Hungaricae 40 
(1976): 65-70; Wagner, Zoltan, pp. 40-41. Bay, Life is Stronger, pp. 103-124, describes the looting and dismantling 
of the Tungsram works by armed agents of the Soviet Union. 

28. DeWitt, telephone conversation, 14 June 1993; DeWitt biographical sketch, HL Diana 46 (04), 
HAUSACEC; Wagner, Zoltan, p. 49; Wagner, Fifty Years, p. 2. 

Among the others were Thomas Gold, Von Eshleman, and A.C. Bernard Lovell. Gold, retired Cornell 
University professor of astronomy, claims to have proposed a lunar radar experiment to the British Admiralty 
during World War II; Eshleman, Stanford University professor of electrical engineering, unsuccessfully attempt- 
ed a lunar radar experiment aboard the U.S.S. Missouri in 1946, while returning from the war; and Lovell pro- 
posed a lunar bounce experiment in a paper of May 1946. Gold 14 December 1993, Eshleman 9 May 1994, and 
Lovell, "Astronomer by Chance" manuscript, February 1988, Lovell materials, p. 183. 

Even earlier, during the 1920s, the Navy unsuccessfully attempted to bounce a 32-KHz, 500-watt radio sig- 
nal off the Moon. A. Hoyt Taylor, Radio Reminiscences: A Half Century (Washington: NRL, 1948) , p. 133. 1 am grate- 
ful to Louis Brown for pointing out this reference. 

29. See DeVorkin, passim. 

30. A.M. Skellett, The Effect of Meteors on Radio Transmission through the Kennelly-Heaviside Layer," 
Physical Review 37 (1931): 1668; Skellett, The Ionizing Effect of Meteors," Proceedings of the Institute of Radio 
Engineers 23 (1935): 132-149. Skellett was a part-time graduate student in astronomy at Princeton University and 
an employee of Bell Telephone Laboratories, New York City. The research described in this article came out of 
a study of the American Telegraph and Telephone Company transatlantic short-wave telephone circuits in 
1930-1932, and how they were affected by meteor ionization. DeVorkin, p. 275. 



A METEORIC START 1 3 



the Air Ministry to study meteors immediately after World War II. They concluded that 
meteors caused abnormal bursts of ionization as they passed through the ionosphere. 31 

During the war, the military had investigated meteor trails with radar. When the 
Germans started bombarding London with V2 rockets, the Army's gun-laying radars were 
hastily pressed into service to detect the radar reflections from the rockets during their 
flight in order to give some warning of their arrival. In many cases alarms were sounded, 
but no rockets were aloft. James S. Hey, a physicist with the Operational Research Group, 
was charged with investigating these mistaken sightings. He believed that the false echoes 
probably originated in the ionosphere and might be associated with meteors. 

Hey began studying the impact of meteors on the ionosphere in October 1944, using 
Army radar equipment at several locations until the end of the war. The Operational 
Research Group, Hey, G. S. Stewart (electrical engineer), S. J. Parsons (electrical and 
mechanical engineer), and J. W. Phillips (mathematician), found a correlation between 
visual sightings and radar echoes during the Giacobinid meteor shower of October 1946. 
Moreover, by using an improved photographic technique that better captured the echoes 
on the radar screen, they were able to determine the velocity of the meteors. 

Neither Hey nor Appleton pursued their radar investigations of meteors. During the 
war, Hey had detected radio emissions from the Sun and the first discrete source of radio 
emission outside the solar system in the direction of Cygnus. He left the Operational 
Research Group for the Royal Radar Establishment at Malvern, where he and his col- 
leagues carried on research in radio astronomy. Appleton, by 1946 a Nobel Laureate and 
Secretary of the Department of Scientific and Industrial Research, also became thor- 
oughly involved in the development of radio astronomy and became a member of the 
Radio Astronomy Committee of the Royal Astronomical Society in 1949. 32 

Radar astronomy, however, did gain a foothold in Britain at the University of 
Manchester under A. C. (later Sir) Bernard Lovell, director of the University's Jodrell 
Bank Experimental Station. During the war, Lovell had been one of many scientists work- 
ing on microwave radar. 33 His superior, the head of the Physics Department, was Patrick 
M. S. Blackett, a member of the Committee for the Scientific Survey of Air Defence that 
approved Watson-Watt's radar memorandum. With the help of Hey and Parsons, Lovell 
borrowed some Army radar equipment. Finding too much interference in Manchester, he 
moved to the University's botanical research gardens, which became the Jodrell Bank 
Experimental Station. Lovell equipped the station with complete war-surplus radar sys- 
tems, such as a 4.2-meter gun-laying radar and a mobile Park Royal radar. He purchased 
at rock-bottom prices or borrowed the radars from the Air Ministry, Army, and Navy, 
which were discarding the equipment down mine shafts. 



31. Appleton and R. Naismith, "The Radio Detection of Meteor Trails and Allied Phenomena," 
Proceeding of the Physical Society 59 (1947): 461-473; James S. Hey and G.S. Stewart, "Radar Observations of 
Meteors," Proceedings of the Physical Society 59 (1947): 858; Lovell, Meteor Astronomy (Oxford: Clarendon Press, 
1954), pp. 23-24. 

32. Hey, The Evolution of Radio Astronomy (New York: Science History Publications, 1973) , pp. 19-23 and 
33-34; Lovell, The Story of Jodrell Bank (London: Oxford University Press, 1968), p. 5; Hey, Stewart, and SJ. 
Parsons, "Radar Observations of the Giacobinid Meteor Shower," Monthly Notices of the Royal Astronomical Society 
107 (1947): 176-183; Hey and Stewart, "Radar Observations of Meteors," Proceedings of the Physical Society 59 
(1947): 858-860 and 881-882; Hey, The Radio Universe (New York: Pergamon Press, 1971), pp. 131-134; Lovell, 
Meteor Astronomy, pp. 28-29 and 50-52; Peter Robertson, Beyond Southern Skies: Radio Astronomy and the Parkes 
Telescope (New York: Cambridge University Press, 1992), p. 39; Dudley Saward, Bernard Lovell, a Biography 
(London: Robert Hale, 1984), pp. 142-145; David O. Edge and Michael J. Mulkay, Astronomy Transformed: The 
Emergence of Radio Astronomy in Britain (New York: Wiley, 1976), pp. 12-14. For a brief historical overview of the 
Royal Radar Establishment, see Ernest H. Pulley, "History of the RSRE," RSRE Research Review 9 (1985): 165-174; 
and D.H. Tomin, "The RSRE: A Brief History from Earliest Times to Present Day," lEEReviewM (1988) : 403-407. 
This major applied sciene institution deserves a more rigorously researched history. 

33. See Lovell, Echoes of War: The Story of //^S Radar (Bristol: Adam Hilger, 1991). Lovell's wartime 
records are stored at the Imperial War Museum, Lambeth Road, London. 



14 



TO SEE THE UNSEEN 




Figure 3 

Thejodrell Bank staff 1951 in front of the 4.2-meter searchlight aerial used in some meteor radar experiments. Sir Bernard 
Lavell is in the center front. (Courtesy of the Director of the Nuffteld Radio Astronomy Laboratories, Jodrell Bank.) 

Originally, Lovell wanted to undertake research on cosmic rays, which had been 
Blackett's interest, too. One of the primary research objectives of the Jodrell Bank facility, 
as well as one of the fundamental reasons for its founding, was cosmic ray research. Indeed, 
the interest in cosmic ray research also lay behind the design and construction of the 
76-meter (250-ft) Jodrell Bank telescope. The search for cosmic rays never succeeded, how- 
ever; Blackett and Lovell had introduced a significant error into their initial calculations. 

Fortuitously, though, in the course of looking for cosmic rays, Lovell came to realize 
that they were receiving echoes from meteor ionization trails, and his small group of 
Jodrell Bank investigators began to concentrate on this more fertile line of research. 
Nicolai Herlofson, a Norwegian meteorologist who had recently joined the Department 
of Physics, put Lovell in contact with the director of the Meteor Section of the British 
Astronomical Association, J. P. Manning Prentice, a lawyer and amateur astronomer with 
a passion for meteors. Also joining the Jodrell Bank team was John A. Clegg, a physics 
teacher whom Lovell had known during the war. Clegg was a doctoral candidate at the 
University of Manchester and an expert in antenna design. He remained at Jodrell Bank 
until 1951 and eventually landed a position teaching physics in Nigeria. Clegg converted 
an Army searchlight into a radar antenna for studying meteors. 34 



34. Lovell 11 January 1994; Lovell, Jodrell Bank, pp. 5-8, 10; Lovell, Meteor Astronomy, pp. 55-63; Edge 
and Mulkay, pp. 15-16; Saward, pp. 129-131; R.H. Brown and Lovell, "Large Radio Telescopes and their Use in 
Radio Astronomy," Vistas in Astronomy 1 (1955): 542-560; Blackett and Lovell, "Radio Echoes and Cosmic Ray 
Showers," Proceedings of the Royal Society of London ser. A, vol. 177 (1941): 183-186; and Lovell, "The Blackett- 
Eckersley-Lovell Correspondence of World War II and the Origin of Jodrell Bank," Notes and Records of the Royal 
Society of London 47 ( 1993) : 1 19-131. For documents relating to equipment on loan from the Ministry of Aviation, 
the War Office, the Royal Radar Establishment, the Admiralty, and the Air Ministry as late as the 1960s, see 
10/51, "Accounts, "JBA. 



A METEORIC START 15 



The small group of professional and amateur scientists began radar observations of 
the Perseid meteor showers in late July and August 1946. When Prentice spotted a mete- 
or, he shouted. His sightings usually, though not always, correlated with an echo on the 
radar screen. Lovell thought that the radar echoes that did not correlate with Prentice's 
sightings might have been ionization trails created by cosmic ray showers. He did not 
believe, initially, that the radar might be detecting meteors too small to be seen by the 
human eye. 

The next opportunity for a radar study of meteors came on the night of 9 October 
1946, when the Earth crossed the orbit of the Giacobini-Zinner comet. Astronomers antic- 
ipated a spectacular meteor shower. A motion picture camera captured the radar echoes 
on film. The shower peaked around 3 A.M.; a radar echo rate of nearly a thousand mete- 
ors per hour was recorded. Lovell recalled that "the spectacle was memorable. It was like 
a great array of rockets coming towards one." 35 

The dramatic correlation of the echo rate with the meteors visible in the sky finally 
convinced Lovell and everyone else that the radar echoes came from meteor ionization 
trails, although it was equally obvious that many peculiarities needed to be investigated. 
The Jodrell Bank researchers learned that the best results were obtained when the aerial 
was positioned at a right angle to the radiant, the point in the sky from which meteor 
showers appear to emanate. When the aerial was pointed at the radiant, the echoes on the 
cathode-ray tube disappeared almost completely. 36 

Next joining the Jodrell Bank meteor group, in December 1946, was a doctoral 
student from New Zealand, Clifton D. Ellyett, followed in January 1947 by a Cambridge 
graduate, John G. Davies. Nicolai Herlofson developed a model of meteor trail ionization 
that Davies and Ellyett used to calculate meteor velocities based on the diffraction pattern 
produced during the formation of meteor trails. Clegg devised a radar technique for 
determining their radiant. 37 

At this point, the Jodrell Bank investigators had powerful radar techniques for study- 
ing meteors that were unavailable elsewhere, particularly the ability to detect and study 
previously unknown and unobservable daytime meteor showers. Lovell and his colleagues 
now became aware of the dispute over the nature of meteors and decided to attempt its 
resolution with these techniques. 38 

Astronomers specializing in meteors were concerned with the nature of sporadic 
meteors. One type of meteor enters the atmosphere from what appears to be a single 
point, the radiant. Most meteors, however, are not part of a shower, but appear to arrive 
irregularly from all directions and are called sporadic meteors. Most astronomers believed 
that sporadic meteors came from interstellar space; others argued that they were part of 
the solar system. 

The debate could be resolved by determining the paths of sporadic meteors. If they 
followed parabolic or elliptical paths, they orbited the Sun; if their orbit were hyperbolic, 
they had an interstellar origin. The paths of sporadic meteors could be determined by an 
accurate measurement of both their velocities and radiants, but optical means were insuf- 
ficiently precise to give unambiguous results. Fred L. Whipple, future director of the 



35. Lovell 1 1 January 1994; Lovell, Jodrell Bank, pp. 7-8, 10. 

36. Lovell 1 1 January 1994; Lovell,/odre// Bank, pp. 8-10; Lovell, Clegg, and Congreve J. Banwell, "Radio 
Echo Observations of the Giacobinid Meteors 1946," Monthly Notices of the Royal Astronomical Society 107 (1947): 
164-175. Banwell was a New Zealand veteran of the Telecommunications Research Establishment wartime radar 
effort and an expert on receiver electronics. 

37. Saward, p. 137; Herlofson, The Theory of Meteor Ionization," Reports on Progress in Physics 11 
( 1946-47) : 444-454; Ellyett and Davies, "Velocity of Meteors Measured by Diffraction of Radio Waves from Trails 
during Formation," Nature 161 (1948): 596-597; Clegg, "Determination of Meteor Radiants by Observation of 
Radio Echoes from Meteor Trails," Philosophical Magazine ser. 7, vol. 39 ( 1948) : 577-594; Davies and Lovell, "Radio 
Echo Studies of Meteors," Vistas in Astronomy 1 (1955): 585-598, provides a summary of meteor research at Jodrell 
Bank. 

38. IJQ\C\\, JodreU Bank, p. 12; Lovell, Meteor Astronomy, pp. 358-383. 



1 6 TO SEE THE UNSEEN 



Harvard College Observatory, a leading center of United States meteor research, attempt- 
ed state-of-the-art optical studies of meteors with the Super Schmidt camera, but the first 
one was not operational until May 1951, at Las Cruces, New Mexico. 39 

Radar astronomers thus attempted to accomplish what optical methods had failed to 
achieve. Such has been the pattern of radar astronomy to the present. Between 1948 and 
1950, Lovell, Davies, and Mary Almond, a doctoral student, undertook a long series of spo- 
radic meteor velocity measurements. They found no evidence for a significant hyperbolic 
velocity component; that is, there was no evidence for sporadic meteors coming from 
interstellar space. They then extended their work to fainter and smaller meteors with sim- 
ilar results. 

The Jodrell Bank radar meteor studies determined unambiguously that meteors 
form part of the solar system. As Whipple declared in 1955, "We may now accept as proven 
the fact that bodies moving in hyperbolic orbits about the sun play no important role in 
producing meteoric phenomena brighter than about the 8th effective magnitude." 40 
Astronomers describe the brightness of a body in terms of magnitude; the larger the mag- 
nitude, the fainter the body. 

The highly convincing evidence of the Jodrell Bank scientists was corroborated by 
Canadian radar research carried out by researchers of the Radio and Electrical 
Engineering Division of the National Research Council under Donald W. R. McKinley. 
McKinley had joined the Council's Radio Section (later Branch) before World War II and, 
like Lovell, had participated actively in wartime radar work. 

McKinley conducted his meteor research with radars built around Ottawa in 1947 
and 1948 as part of various National Research Council laboratories, such as the Flight 
Research Center at Arnprior Airport. Earle L. R. Webb, Radio and Electrical Engineering 
Division of the National Research Council, supervised the design, construction, and oper- 
ation of the radar equipment. From as early as the summer of 1947, the Canadian radar 
studies were undertaken jointly with Peter M. Millman of the Dominion Observatory. 
They coordinated spectrographic, photographic, radar, and visual observations. The 
National Research Council investigators employed the Jodrell Bank technique to deter- 
mine meteor velocities, a benefit of following in the footsteps of the British. 41 

Their first radar observations took place during the Perseid shower of August 1947, 
as the first radar station reached completion. Later studies collected data from the 
Geminid shower of December 1947 and the Lyrid shower of April 1948, with more radar 
stations brought into play as they became available. Following the success of Jodrell Bank, 



39. Ron Doel, "Unpacking a Myth: Interdisciplinary Research and the Growth of Solar System 
Astronomy, 1920-1958," Ph.D. diss. Princeton University, 1990, pp. 33-35, 42-44 and 108-111; DeVorkin, pp. 96, 
273, 278 and 293; Luigi G. Jacchia and Whipple, The Harvard Photographic Meteor Programme," Vistas in 
Astronomy 2 (1956): 982-994; Whipple, "Meteors and the Earth's Upper Atmosphere," Reviews of Modern Physics 
15 (1943): 246-264; Whipple, "The Baker Super-Schmidt Meteor Cameras," The Astronomical Journal 56 (1951): 
144-145, states that the first such camera was installed in New Mexico in May 1951. Determining the origin of 
meteors was not the primary interest of Harvard research. 

40. Whipple, "Some Problems of Meteor Astronomy," in H. C. Van de Hulst, ed., Radio Astronomy 
(Cambridge: Cambridge University Press, 1957), p. 376; Almond, Davies, and Lovell, "The Velocity Distribution 
of Sporadic Meteors," Monthly Notices of the Royal Astronomical Society III (1951): 585-608; 112 (1952): 21-39; 113 
(1953): 411-427. The meteor studies at Jodrell Bank were continued into later years. See, for instance, I. C. 
Browne and T. R. Kaiser, "The Radio Echo from the Head of Meteor Trails,"/0urn/ of Atmospheric and Terrestrial 
Physics 4 (1953): 1-4. 

41. W. E. Knowles Middleton, Radar Development in Canada: The Radio Branch of the National Research 
Council of Canada, 1939-1946 (Waterloo, Ontario: Wilfred Laurier University Press, 1981), pp. 18, 25, 27, 
106-109; Millman and McKinley, "A Note on Four Complex Meteor Radar Echoes," Journal of the Royal 
Astronomical Society of Canada 42 (1948): 122; McKinley and Millman, "A Phenomenological Theory of Radar 
Echoes from Meteors," Proceedings of the Institute of Radio Engineers 37 (1949): 364-375; McKinley and Millman, 
"Determination of the Elements of Meteor Paths from Radar Observations," Canadian Journal of Research A27 
(1949): 53-67; McKinley, "Deceleration and Ionizing Efficiency of Radar Meteors, "Journal of Applied Physics 22 
(1951): 203; McKinley, Meteor Science and Engineering (New York: McGraw-Hill, 1961), p. 20; Lovell, Meteor 
Astronomy, pp. 52-55. 



A METEORIC START 17 



McKinley's group initiated their own study of sporadic meteors. By 1951, with data on 
10,933 sporadic meteors, McKinley's group reached the same conclusion as their British 
colleagues: meteors were part of the solar system. Soon, radar techniques became an inte- 
gral part of Canadian meteor research with the establishment in 1957 of the National 
Research Council Springhill Meteor Observatory outside Ottawa. The Observatory con- 
centrated on scientific meteor research with radar, visual, photographic, and spectro- 
scopic methods. 42 

These meteor studies at Jodrell Bank and the National Research Council, and only 
at those institutions, arose from the union of radar and astronomy; they were the begin- 
nings of radar astronomy. Radar studies of meteors were not limited to Jodrell Bank and 
the National Research Council, however. With support from the National Bureau of 
Standards, in 1957 Harvard College Observatory initiated a radar meteor project under 
the direction of Fred Whipple. Furthermore, radar continues today as an integral and vital 
part of worldwide meteor research. Its forte is the ability to determine orbits better than 
any other technique. In the last five years, a number of recently built radars have studied 
meteors in Britain (MST Radar, Aberytswyth, Wales), New Zealand (AMOR, Meteor Orbit 
Radar, Christchurch), and Japan (MU Radar, Shigaraki), not to mention earlier work in 
Czechoslovakia and Sweden. 43 

Unlike the Jodrell Bank and National Research Council cases, the radar meteor stud- 
ies started in the United States in the early 1950s were driven by civilian scientists doing 
ionospheric and communications research and by the military's desire for jam-proof^ 
point-to-point secure communications. While various military laboratories undertook 
their own research programs, most of the civilian U.S. radar meteor research was carried 
out at Stanford University and the National Bureau of Standards, where investigators fruit- 
fully cross-fertilized ionospheric and military communications research. The Stanford 
case is worth examining not only for its later connections to radar astronomy, but also for 
its pioneering radar study of the Sun that arose out of an interest in ionospheric and radio 
propagation research. 

In contrast to the Stanford work, many radar meteor experiments carried out in the 
United States in the 1940s were unique events. As early as August and November 1944, for 
instance, workers in the Federal Communications Commission Engineering Department 
associated visual observations of meteors and radio bursts. In January 1946, Oliver Perry 
Ferrell of the Signal Corps reported using a Signal Corps SCR-270B radar to detect mete- 
or ionization trails. 44 The major radar meteor event in the United States and elsewhere, 



42. Millman, McKinley, and M. S. Burland, "Combined Radar, Photographic, and Visual Observations 
of the 1947 Perseid Meteor Shower," Nature 161 (1948): 278-280; McKinley and Millman, "Determination of the 
Elements," p. 54; Millman and McKinley, "A Note," pp. 121-130; McKinley, "Meteor Velocities Determined by 
Radio Observations," The Astrophysics Journal US (1951): 225-267; F. R. Park, "An Observatory for the Study of 
Meteors," Engineering Journal 41 (1958): 68-70. 

43. Whipple, "Recent Harvard-Smithsonian Meteoric Results," Transactions of the IAU 10 (1960): 
345-350; Jack W. Baggaley and Andrew D. Taylor, "Radar Meteor Orbital Structure of Southern Hemisphere 
Cometary Dust Streams," pp. 33-36 in Alan W. Harris and Edward Bowell, eds., Asteroids, Comets, Meteors 1991 
(Houston: Lunar and Planetary Institute, 1992) ; Baggaley, Duncan I. Steel, and Taylor, "A Southern Hemisphere 
Radar Meteor Orbit Survey," pp. 37-40 in ibidem; William Jones and S. P. Kingsley, "Observations of Meteors by 
MST Radar," pp. 281-284 in ibidem; Jun-ichi Wattanabe, Tsuko Nakamura, T. Tsuda, M. Tsutsumi, A. Miyashita, 
and M. Yoshikawa, "Meteor Mapping with MU Radar," pp. 625-627 in ibidem. The MST Radar and the AMOR 
were newly commissioned in 1990. The MU Radar is intended primarily for atmospheric research. 

For the meteor radar research in Sweden and Czechoslovakia, see B. A. Lindblad and M. Simek, 
"Structure and Activity of Perseid Meteor Stream from Radar Observations, 1956-1978," pp. 431-434 in Claes- 
Ingva Lagerkvist and Hans Rickman, eds., Asteroids, Comets, Meteors (Uppsala: Uppsala University, 1983); A. 
Hajduk and G. Cevolani, "Variations in Radar Reflections from Meteor Trains and Physical Properties of 
Meteoroids," pp. 527-530 in Lagerkvist, H. Rickman, Lindblad, and M. Lindgren, Asteroids, Comets, Meteors III 
(Uppsala: Uppsala University, 1989); Simek and Lindblad, The Activity Curve of the Perseid Meteor Stream as 
Determined from Short Duration Meteor Radar Echoes," pp. 567-570 in ibidem. 

44. Ferrell, "Meteoric Impact Ionization Observed on Radar Oscilloscopes," Physical Review 2d sen, vol. 
69 (1946): 32-33; Lovell, Meteor Astronomy, p. 28. 



1 8 TO SEE THE UNSEEN 



however, was the spectacular meteor shower associated with the Giacobini-Zinner comet. 

On the night of 9 October 1946, 21 Army radars were aimed toward the sky in order 
to observe any unusual phenomena. The Signal Corps organized the experiment, which 
fit nicely with their mission of developing missile detection and ranging capabilities. The 
equipment was operated by volunteer crews of the Army ground forces, the Army Air 
Forces, and the Signal Corps located across the country in Idaho, New Mexico, Texas, and 
New Jersey. For mainly meteorological reasons, only the Signal Corps SCR-270 radar suc- 
cessfully detected meteor ionization trails. No attempt was made to correlate visual obser- 
vations and radar echoes. A Princeton University undergraduate, Francis B. Shaffer, who 
had received radar training in the Navy, analyzed photographs of the radar screen echoes 
at the Signal Corps laboratory in Belmar, New Jersey. 

This was the first attempt to utilize microwave radars to detect astronomical objects. 
The equipment operated at 1,200 MHz (25 cm), 3,000 MHz (10 cm), and 10,000 MHz (3 
cm) , frequencies in the L, S, and X radar bands that radar astronomy later used. "On the 
basis of this night's experiments," the Signal Corps experimenters decided, "we cannot 
conclude that microwave radars do not detect meteor-formed ion clouds." 45 

In contrast to the Signal Corps experiment, radar meteor studies formed part of 
ongoing research at the National Bureau of Standards. Organized from the Bureau's 
Radio Section in May 1946 and located at Sterling, Virginia, the Central Radio 
Propagation Laboratory (CRPL) division had three laboratories, one of which concerned 
itself exclusively with ionospheric research and radio propagation and was especially inter- 
ested in the impact of meteors on the ionosphere. In October 1946, Victor C. Pineo and 
others associated with the CRPL used a borrowed SCR-270-D Signal Corps radar to 
observe the Giacobinid meteor shower. Over the next five years, Pineo continued research 
on the effects of meteors on the ionosphere, using a standard ionospheric research instru- 
ment called an ionosonde and publishing his results in Science. 

Pineo's interest was in ionospheric physics, not astronomy. Underwriting his 
research at the Ionospheric Research Section of the National Bureau of Standards was the 
Air Force Cambridge Research Center (known later as the Cambridge Research 
Laboratories and today as Phillips Laboratory) . His meteor work did not contribute to 
knowledge about the origin of meteors, as such work had in Britain and Canada, but it 
supported efforts to create secure military communications using meteor ionization 
trails. 46 Also, it related to similar research being carried out concurrently at Stanford 
University. 

The 1946 CRPL experiment, in fact, had been suggested by Robert A. Helliwell of 
the Stanford Radio Propagation Laboratory (SRPL) . Frederick E. Terman, who had head- 
ed the Harvard Radio Research Laboratory and its radar counter measures research dur- 
ing the war, "virtually organized radio and electronic engineering on the West Coast" as 



45. Signal Corps Engineering Laboratories, "Postwar Research and Development Program of the Signal 
Corps Engineering Laboratories, 1945," (Signal Corps, 1945), "Postwar R&D Program," HL R&D, HAUSACEC; 
John Q. Stewart, Michael Ference, John J. Slattery, Harold A. Zahl, "Radar Observations of the Draconids," Sky 
and Telescope 6 (March 1947) : 35. They reported their earlier results in a paper, "Radar Observations of the 
Giacobinid Meteors," read before the December 1946 meeting of the American Astronomical Society in Boston. 
HL Diana 46 (26), HAUSACEC. 

46. Wilbert F. Snyder and Charles L. Bragaw, Achievement in Radio: Seventy Yean of Radio Science, 
Technology, Standards, and Measurement at the National Bureau of Standards (Boulder: National Bureau of Standards, 
1986), pp. 461-465; Ross Bateman, A. G. McNish, and Pineo, "Radar Observations during Meteor Showers, 9 
October 1946," Science 104 (1946): 434-435; Pineo, "Relation of Sporadic E Reflection and Meteoric Ionization," 
Science 110 (1949): 280-283; Pineo, "A Comparison of Meteor Activity with Occurrence of Sporadic-E 
Reflections," Science 112 (1950): 5051; Pineo and T. H. Gautier, "The Wave-Frequency Dependence of the 
Duration of Radar-Type Echoes from Meteor Trails," Science 114 (1951): 460-462. Other articles by Pineo on his 
ionospheric research can be found in Laurence A. Manning, Bibliography of the Ionosphere: An Annotated Survey 
through I960 (Stanford: Stanford University Press, 1962), pp. 421-423. 



A METEORIC START 19 



Stanford Dean of Engineering, according to historian C. Stewart Gillmor. Terman nego- 
tiated a contract with the three military services for the funding of a broad range of 
research, including the SRPL's long-standing ionospheric research program. 47 

Helliwell, whose career was built on ionospheric research, was joined at the SRPL by 
Oswald G. Villard, Jr. Villard had earned his engineering degree during the war for the 
design of an ionosphere sounder. As an amateur radio operator in Cambridge, 
Massachusetts, he had noted the interference caused by meteor ionizations at shortwave 
frequencies called Doppler whistles. 48 

In October 1946, during the Giacobinid meteor shower, Helliwell, Villard, Laurence 
A. Manning, and W. E. Evans, Jr., detected meteor ion trails by listening for Doppler whis- 
tles with radios operating at 15 MHz (20 meters) and 29 MHz (10 meters). Manning then 
developed a method of measuring meteor velocities using the Doppler frequency shift of 
a continuous-wave signal reflected from the ionization trail. Manning, Villard, and Allen 
M. Peterson then applied Manning's technique to a continuous-wave radio study of the 
Perseid meteor shower in August 1948. The initial Stanford technique was significantly 
different from that developed at Jodrell Bank; it relied on continuous-wave radio, rather 
than pulsed radar, echoes. 49 

One of those conducting meteor studies at Stanford was Von R. Eshleman, a gradu- 
ate student in electrical engineering who worked under both Manning and Villard. While 
serving in the Navy during World War II, Eshleman had studied, then taught, radar at the 
Navy's radar electronics school in Washington, DC. In 1946, while returning from the war 
on the U.S.S. Missouri, Eshleman unsuccessfully attempted to bounce radar waves off the 
Moon using the ship's radar. Support for his graduate research at Stanford came through 
contracts between the University and both the Office of Naval Research and the Air Force. 

Eshleman 's dissertation considered the theory of detecting meteor ionization trails 
and its application in actual experiments. Unlike the British and Canadian meteor stud- 
ies, the primary research interest of Eshleman, Manning, Villard, and the other Stanford 
investigators was information about the winds and turbulence in the upper atmosphere. 
Their investigations of meteor velocities, the length of ionized meteor trails, and the fad- 
ing and polarization of meteor echoes were part of that larger research interest, while 
Eshleman 's dissertation was an integral part of the meteor research program. 

Eshleman also considered the use of meteor ionization trails for secure military com- 
munications. His dissertation did not explicitly state that application, which he took up 
after completing the thesis. The Air Force supported the Stanford meteor research main- 
ly to use meteor ionization trails for secure, point-to-point communications. The Stanford 
meteor research thus served a variety of scientific and military purposes simultaneously. 50 



47. Gillmor, "Federal Funding and Knowledge Growth in Ionospheric Physics, 1945-1981," Social Studies 
of Science 16 (1986): 124. 

48. Oswald G. Villard, Jr., "Listening in on the Stars," QST 30 (January, 1946): 59-60, 120 and 122; 
Helliwell, Whistlers and Related Ionospheric Phenomena (Stanford: Stanford University Press, 1965), pp. 11-23; 
Leslie, p. 58; Gillmor, "Federal Funding," p. 129. 

49. Manning, Helliwell, Villard, and Evans, "On the Detection of Meteors by Radio," Physical Review 70 
( 1946) : 767-768; Manning, "The Theory of the Radio Detection of Meteors,"7ourna/ of Applied Physics 19 ( 1948) : 
689-699: Manning, Villard, and Peterson, "Radio Doppler Investigation of Meteoric Heights and Velocities," 
Journal of Applied Physics 20 ( 1949) : 475-479; Von R. Eshleman, "The Effect of Radar Wavelength on Meteor Echo 
Rate," Transactions of the Institute of Radio Engineers 1 (1953): 37-42. DeVorkin, pp. 287-288, points out that, when 
given an opportunity to make radio observations in coordination with rocket flights, Stanford declined. 

50. Eshleman 9 May 1994; Eshleman, The Mechanism of Radio Reflections from Meteoric Ionization," 
Ph.D. diss., Stanford University, 1952; Eshleman, The Mechanism of Radio Reflections from Meteoric Ionization, 
Technical Report no. 49 (Stanford: Stanford Electronics Research Laboratory, 15 July 1952), pp. ii-iii and 3; 
Manning, "Meteoric Radio Echoes," Transactions of the Institute of Radio Engineers 2 (1954): 82-90; Manning and 
Eshleman, "Meteors in the Ionosphere," Proceedings of the Institute of Radio Engineers 47 (1959): 186-199. 



20 TO SEE THE UNSEEN 



The meteor research carried out at Stanford had nontrivial consequences. 
Eshleman's dissertation has continued to provide the theoretical foundation of modern 
meteor burst communications, a communication mode that promises to function even 
after a nuclear holocaust has rendered useless all normal wireless communications. The 
pioneering work at Stanford, the National Bureau of Standards, and the Air Force 
Cambridge Research Laboratories received new attention in the 1980s, when the Space 
Defense Initiative ("Star Wars") revitalized interest in using meteor ionization trails for 
classified communications. Non-military applications of meteor burst communications 
also have arisen in recent years. 51 

Early meteor burst communications research was not limited to Stanford and the 
National Bureau of Standards. American military funding of early meteor burst commu- 
nications research extended beyond its shores to Britain. Historians of Jodrell Bank radio 
astronomy and meteor radar research stated that radio astronomy had surpassed meteor 
studies at the observatory by 1955. However, that meteor work persisted until 1964 
through a contract with the U.S. Air Force, though as a cover for classified military 
research. 52 

Auroras provided additional radar targets in the 1950s. A major initiator of radar 
auroral studies was Jodrell Bank. As early as August 1947, while conducting meteor 
research, the Jodrell Bank scientists Lovell, Clegg, and Ellyett received echoes from an 
aurora display. Arnold Aspinall and G. S. Hawkins then continued the radar auroral stud- 
ies at Jodrell Bank in collaboration with W. B. Housman, Director of the Aurora Section 
of the British Astronomy Association, and the aurora observers of that Section. In Canada, 
McKinley and Millman also observed an aurora during their meteor research in April 
1948.S3 

The problem with bouncing radar waves off an aurora was determining the reflect- 
ing point. Researchers in the University of Saskatchewan Physics Department (B. W. 
Currie, P. A. Forsyth, and F. E. Vawter) initiated a systematic study of auroral radar reflec- 
tions in 1948, with funding from the Defense Research Board of Canada. Radar equip- 
ment was lent by the U.S. Air Force Cambridge Research Center and modified by the 
Radio and Electrical Engineering Division of the National Research Council. Forsyth had 
completed a dissertation on auroras at McGill University and was an employee of the 
Defense Research Board's Telecommunications Establishment on loan to die University 
of Saskatchewan for the project. The Saskatchewan researchers discovered that the echoes 
bounced off small, intensely ionized regions in the aurora. 54 

Other aurora researchers, especially in Sweden and Norway, took up radar studies. 
In Sweden, Gotha Hellgren and Johan Meos of the Chalmers University of Technology 



51. Robert Desourdis, telephone conversation, 22 September 1994; Donald Spector, telephone conver- 
sation, 22 September 1994; Donald L. Schilling, ed., Meteor Burst Communications: Theory and Practice (New York: 
Wiley, 1993); Jacob Z. Schanker, Meteor Bunt Communications (Boston: Artech House, 1990). For a civilian use of 
meteor burst communications, see Henry S. Santeford, Meteor Burst Communication System: Alaska Winter Field Test 
Program (Silver Spring, MD: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, 
National Weather Service, Office of Hydrology, 1976). 

52. Lovell 11 January 1994; 7 and 8/55, "Accounts, "JBA; Lovell, "Astronomer by Chance," typed man- 
uscript, February 1988, p. 376, Lovell materials; Lovell, Jodrell Bank, p. 157; G. Nigel Gilbert, "The Development 
of Science and Scientific Knowledge: The Case of Radar Meteor Research," in Gerard Lemaine, Roy Macleod, 
Michael Mulkay, and Peter Weingart, eds., Perspectives on the Emergence of Scientific Disciplines (Chicago: Aldine, 
1976), p. 191; Edge and Mulkay, pp. 330-331. 

53. Lovell, Clegg, and Ellyett, "Radio Echoes from the Aurora Borealis," Nature 160 ( 1947) : 372; Aspinall 
and Hawkins, "Radio Echo Reflections from the Aurora Eorealia," Journal of the British Astronomical Association 60 
(1950): 130-135; various materials in File Group "International Geophysical Year," Box 1, File 4, JBA; McKinley 
and Millman, "Long Duration Echoes from Aurora, Meteors, and Ionospheric Back-Scatter," Canadian Journal of 
PhysicsBl (1953): 171-181. 

54. Currie, Forsyth, and Vawter, "Radio Reflections from Aurora," Journal of Geophysical Research 58 
(1953): 179-200. 



A METEORIC START 21 



Research Laboratory of Electronics in Gothenburg decided to conduct radar studies of 
auroras as part of their ionospheric research program. Beginning in May 1951, the Radio 
Wave Propagation Laboratory of the Kiruna Geophysical Observatory undertook round- 
the-clock observations of auroras with a 30.3-MHz (10-meter) radar. In Norway, Leiv 
Harang, who had observed radar echoes from an aurora as early as 1940, and B. 
Landmark observed auroras with radars lent by the Norwegian Defense Research 
Establishment and installed at Oslo (Kjeller) and Tromso, where a permanent center for 
radar investigation of auroras was created later. 55 

These and subsequent radar investigations changed the way scientists studied auro- 
ras, which had been almost entirely by visual means up to about 1950. Permanent auroral 
observatories located at high latitudes, such as those at Oslo and Tromso in Norway, at 
Kiruna in Sweden, and at Saskatoon in Saskatchewan, integrated radar into a spectrum of 
research instruments that included spectroscopy, photography, balloons, and sounding 
rockets. The International Geophysical Year, 1957-1958, was appropriately timed to fur- 
ther radar auroral research; it coincided with extremely high sunspot and auroral activity, 
such as the displays visible from Mexico in September 1957 and the "Great Red Aurora" 
of 10 February 1958. Among those participating in the radar aurora and meteor studies 
associated with the International Geophysical Year activities were three Jodrell Bank stu- 
dents and staff who joined the Royal Society expedition to Halley Bay, Antarctica. 56 



To the Moon Again 



The auroral and meteor radar studies carried out in the wake of the lunar radar 
experiments of DeWitt and Bay were, in essence, ionospheric studies. While the causes of 
auroras and meteor ionization trails arise outside the Earth's atmosphere, the phenome- 
na themselves are essentially ionospheric. At Jodrell Bank, meteor and auroral studies pro- 
vided the initial impetus, but certainly not the sustaining force, for the creation of an 
ongoing radar astronomy program. That sustaining force came from lunar studies. 
However, like so much of early radar astronomy, those lunar studies were never far from 
ionospheric research. Indeed, the trailblazing efforts of DeWitt and Bay opened up new 
vistas of ionospheric and communications research using radar echoes from the Moon. 

Historically, scientists had been limited to the underside and lower portion of the 
ionosphere. The discovery of "cosmic noise" by Bell Telephone researcher Karl Jansky in 
1932 suggested that higher frequencies could penetrate the ionosphere. The experiments 
of DeWitt and Bay suggested radar as a means of penetrating the lower regions of the 
ionosphere. DeWitt, moreover, had observed unexpected fluctuations in signal strength 
that lasted several minutes, which he attributed to anomalous ionospheric refraction. 57 
His observations invited further investigation of the question. 

The search for a better explanation of those fluctuations was taken up by a group of 
ionosphericists in the Division of Radiophysics of the Australian Council for Scientific and 
Industrial Research: Frank J. Kerr, C. Alex Shain, and Charles S. Higgins. In 1946, Kerr 
and Shain explored the possibility of obtaining radar echoes from meteors, following the 



55. Hellgren and Meos, "Localization of Aurorae with 10m High Power Radar Technique, using a 
Rotating Antenna," Tellus 3 (1952): 249-261; Harang and Landmark, "Radio Echoes Observed during Aurorae 
and Geomagnetic Storms using 35 and 74 Mc/s Waves Simultaneously," Journal of Atmospheric and Terrestrial 
Physics 4 (1954): 322-338; ibidem Nature 171 (1953): 1017-1018; Harang and J. Troim, "Studies of Auroral 
Echoes," Planetary and Space Science*) (1961): 33-45 and 105-108. 

56. Jean Van Bladel, Les applications du radar I'astronomie et a la meteorologie (Paris: Gauthier-VHlars, 
1955), pp. 78-80; Neil Bone, The Aurora: Sun-Earth Interactions (New York: Ellis Horwood, 1991), pp. 36, 45-49; 
Alistair Vallance Jones, Aurora (Boston: D. Reidel Publishing Company, 1974), pp. 9, 11 and 27; Lovell, 
"Astronomer by Chance," manuscript, February 1988, p. 201, Lovell materials. 

57. DeWitt and Stodola, p. 239. 



22 TO SEE THE UNSEEN 



example of Lovell in Britain, but Project Diana turned their attention toward the Moon. 
In order to study the fluctuations in signal strength that DeWitt had observed, Kerr, Shain, 
and Higgins put together a rather singular experiment. 

For a transmitter, they used the 20-MHz (15-meter) Radio Australia station, located 
in Shepparton, Victoria, when it was not in use for regular programming to the United 
States and Canada. The receiver was located at the Radiophysics Laboratory, Hornsby, 
New South Wales, a distance of 600 km from the transmitter. Use of this unique system was 
limited to days when three conditions could be met all at the same time: the Moon was 
passing through the station's antenna beams; the transmitter was available; and atmos- 
pheric conditions were favorable. In short, the system was workable about twenty days a 
year. 58 

Kerr, Shain, and Higgins obtained lunar echoes on thirteen out of fifteen attempts. 
The amplitude of the echoes fluctuated considerably over the entire run of tests as well as 
within a single test. Researchers at ITT's Federal Telecommunications Laboratories in 
New York City accounted for the fluctuations observed by DeWitt by positing the existence 
of smooth spots that served as "bounce points" for the reflected energy. Another possibil- 
ity they imagined was the existence of an ionosphere around the Moon. 59 The Australians 
disagreed with the explanations offered by DeWitt and the ITT researchers, but they were 
initially cautious: "It cannot yet be said whether the reductions in intensity and the long- 
period variations are due to ionospheric, lunar or inter-planetary causes." 60 

During a visit to the United States in 1948, J. L. Pawsey, a radio astronomy enthusiast 
also with the Council for Scientific and Industrial Research's Division of Radiophysics, 
arranged a cooperative experiment with the Americans. A number of U.S. organizations 
with an interest in radio, the National Bureau of Standards CRPL, the Radio Corporation 
of America (Riverhead, New York), and the University of Illinois (Urbana), attempted to 
receive Moon echoes simultaneously from Australia, beginning 30 July 1948. Ross 
Bateman (CRPL) acted as American coordinator. The experiment was not a great success. 
The times of the tests (limited by transmitter availability) were all in the middle of the day 
at the receiving points. Echoes were received in America on two occasions, 1 August and 
28 October, and only for short periods in each case. 

Meanwhile, Kerr and Shain continued to study lunar echo fading with the Radio 
Australia transmitter. Based on thirty experiments (with echoes received in twenty-four of 
them) conducted over a year, they now distinguished rapid and slow fading. Kerr and 
Shain proposed that each type of fading had a different cause. Rapid fading resulted from 
the Moon's libration, a slow wobbling motion of the Moon. Irregular movement in the 
ionosphere, they originally suggested, caused the slower fading. 61 Everyone agreed that 
the rapid fading of lunar radar echoes originated in the lunar libration, but the cause of 
slow fading was not so obvious. 

The problem of slow fading was taken up at Jodrell Bank by William A. S. Murray and 
J. K. Hargreaves, who sought an explanation in the ionosphere. Although Lovell had pro- 
posed undertaking lunar radar observations as early as 1946, the first worthwhile results 
were not obtained until the fall of 1953. Hargreaves and Murray photographed and ana- 
lyzed some 50,000 lunar radar echoes at the Jodrell Bank radar telescope in October and 
November 1953 to determine the origin of slow fading. 



58. Kerr, Shain, and Higgins, "Moon Echoes and Penetration of the Ionosphere," Nature 163 (1949): 
310; Kerr and Shain, "Moon Echoes and Transmission through the Ionosphere," ftoceedings oftheIRE39 (1951): 
230; Kerr, "Early Days in Radio and Radar Astronomy in Australia," pp. 136-137 in Sullivan. Kerr and Shain, pp. 
230-232, contains a better description of the system. See also Kerr, "Radio Superrefraction in the Coastal 
Regions of Australia," Australian Journal of Scientific Research, sen A, vol. 1 (1948): 443-463. 

59. D. D. Grieg, S. Metzger, and R. Waer, "Considerations of Moon-Relay Communication," Proceedings 
of the IRE 36 (1 948): 660. 

60. Kerr, Shain, and Higgins, p. 311. 

61. Kerr and Shain, pp. 230-242. 



A METEORIC START 23 



With rare exceptions, nighttime runs showed a steady signal amplitude, while day- 
time runs, especially those within a few hours of sunrise, were marked by severe fading. 
The high correlation between fading and solar activity strongly suggested an ionospheric 
origin. However, Hargreaves and Murray believed that irregularities in the ionosphere 
could not account for slow fading over periods lasting up to an hour. They suggested 
instead that slow fading resulted from Faraday rotation, in which the plane of polarization 
of the radio waves rotated, as they passed through the ionosphere in the presence of the 
Earth's magnetic field. 

Hargreaves and Murray carried out a series of experiments to test their hypothesis in 
March 1954. The transmitter had a horizontally polarized antenna, while the primary feed 
of the receiving antenna consisted of two dipoles mounted at right angles. They switched 
the receiver at short intervals between the vertical and horizontal feeds so that echoes 
would be received in both planes of polarization, a technique that is a standard planetary 
radar practice today. 

As the plane of polarization of the radar waves rotated in the ionosphere, stronger 
echo amplitudes were received by the vertical feed than by the horizontal feed. If no 
Faraday rotation had taken place, both the transmitted and received planes of polariza- 
tion would be the same, that is, horizontal. But Faraday rotation of the plane of polariza- 
tion in the ionosphere had rotated the plane of polarization so that the vertical feed 
received more echo power than the horizontal feed. The results confirmed that slow 
fading was caused, at least in part, by a change in the plane of polarization of the received 
lunar echo. 62 

Murray and Hargreaves soon took positions elsewhere, yet Jodrell Bank continued to 
feature radar astronomy through the persistence of Bernard Lovell. Lovell became entan- 
gled in administrative affairs and the construction of a giant radio telescope, while John 
V. Evans, a research student of Lovell, took over the radar astronomy program. Evans had 
a B.Sc. in physics and had had an interest in electronics engineering since childhood. He 
chose the University of Manchester Physics Department for his doctoral degree, because 
the department, through Lovell, oversaw the Jodrell Bank facility. The facility's heavy 
involvement in radio and radar astronomy, when Evans arrived there on his bicycle in the 
summer of 1954, assured Evans that his interest in electronics engineering would be sated. 

With the approval and full support of Lovell, Evans renewed the studies of lunar 
radar echoes, but first he rebuilt the lunar radar equipment. It was a "poor instrument," 
Evans later recalled, "and barely got echoes from the Moon." After he increased the power 
output from 1 to 10 kilowatts and improved the sensitivity of the receiver by rebuilding the 
front end, Evans took the lunar studies in a new direction. Unlike the majority of Jodrell 
Bank research, Evans's lunar work was underwritten through a contract with the U.S. Air 
Force, which was interested in using the Moon as part of a long-distance communications 
system. 

With his improved radar apparatus, Evans discovered that the Moon overall was a rel- 
atively smooth reflector of radar waves at the wavelength he used (120 MHz; 2.5 meters). 
Later, from the way that the Moon appeared to scatter back radar waves, Evans speculat- 
ed that the lunar surface was covered with small, round objects such as rocks and stones. 
Hargreaves proposed that radar observations at shorter wavelengths should be able to give 
interesting statistical information about the features of the lunar surface. 63 That idea was 



62. Murray and Hargreaves, "Lunar Radio Echoes and the Faraday Effect in the Ionosphere," Nature 173 
(1954): 944-945; Browne, Evans, Hargreaves, and Murray, p. 901; 1/17 "Correspondence Series 7,"JBA; Lovell, 
"Astronomer by Chance," p. 183. 

63. Evans 9 September 1993; Hargreaves, "Radio Observations of the Lunar Surface," Proceedings of the 
Physical Society 73 (1959): 536-537; Evans, "Research on Moon Echo Phenomena," Technical (Final) Report, 1 
May 1956, and earlier reports in 1/4 "Correspondence Series 2,"JBA. 



24 TO SEE THE UNSEEN 



the starting point for the creation of planetary radar techniques that would reveal the sur- 
face characteristics of planets and other moons. 

Experimenters prior to Evans had assumed that the Moon reflected radar waves from 
the whole of its illuminated surface, like light waves. They debated whether the power 
returned to the Earth was reflected from the entire visible disk or from a smaller region. 
The question was important to radar astronomers at Jodrell Bank as well as to military and 
civilian researchers developing Moon-relay communications. 

In March 1957, Evans obtained a series of lunar radar echoes. He photographed 
both the transmitted pulses and their echoes so that he could make a direct comparison 
between the two. Evans also made range measurements of the echoes at the same time. In 
each case, the range of the observed echo was consistent with that of the front edge of the 
Moon. The echoes came not from the entire visible disk but from a smaller portion of the 
lunar surface, that closest to the Earth and known as the subradar point. 64 This discovery 
became fundamental to radar astronomy research. 

Because radar waves reflected off only the foremost edge of the Moon, Evans and 
John H. Thomson (a radio astronomer who had transferred from Cambridge in 1959) 
undertook a series of experiments on the use of the Moon as a passive communication 
relay. Although initial results were "not intelligible," because FM and AM broadcasts tend- 
ed to fade, Lovell bounced Evans' "hello" off the Moon with a Jodrell Bank transmitter 
and receiver during his BBC Reith Lecture of 1958. Several years later, in collaboration 
with the Pye firm, a leading British manufacturer of electronic equipment headquartered 
in Cambridge, and with underwriting from the U.S. Air Force, a Pye transmitter at Jodrell 
Bank was used to send speech and music via the Moon to the Sagamore Hill Radio 
Astronomy Observatory of the Air Force Cambridge Research Center, at Hamilton, 
Massachusetts. The U.S. Air Force thus obtained a successful lunar bounce communica- 
tion experiment at Jodrell Bank for a far smaller sum than that spent by the Naval 
Research Laboratory. 65 

The Moon Bounce 

The lunar communication studies at Jodrell Bank illustrate that astronomy was not 
behind all radar studies of the Moon. Much of the lunar radar work, especially in the 
United States, was performed to test long-distance communication systems in which the 
Moon would serve as a relay. Thus, the experiments of DeWitt and Bay may be said to have 
begun the era of satellite communications. Research on Moon-relay communications sys- 
tems by both military and civilian laboratories eventually drew those institutions into the 
early organizational activities of radar astronomers. After all, both communication 
research and radar astronomy shared an interest in the behavior of radio waves at the 
lunar surface. Hence, a brief look at that research would be informative. 

Before the advent of satellites, wireless communication over long distances was 
achieved by reflecting radio waves off the ionosphere. As transmission frequency 
increased, the ionosphere was penetrated. Long-distance wireless communication at high 
frequencies had to depend on a network of relays, which were expensive and technically 
complex. Using the Moon as a relay appeared to be a low-cost alternative. 66 



64. Evans 9 September 1993; Evans, The Scattering of Radio Waves by the Moon," Proceedings of the 
Physical Society B70 (1957): 1105-1112. 

65. Evans 9 September 1993; Edge and Mulkay, p. 298; Materials in 1/4 "Correspondence Series 2," and 
2/53 "Accounts, "JBA. With NASA funding, Jodrell Bank later participated in the Echo balloon project. 

66. Harold Sobol, "Microwave Communications: An Historical Perspective," IEEE Transactions on 
Microwave Theory and Techniques MTT-32 (1984): 1170-1181. 



A METEORIC START 25 



Reacting to the successes of DeWitt and Bay, researchers at the ITT Federal 
Telecommunications Laboratories, Inc., New York City, planned a lunar relay telecom- 
munication system operating at UHF frequencies (around 50 MHz; 6 meters) to provide 
radio telephone communications between New York and Paris. If such a system could be 
made to work, it would provide ITT with a means to compete with transatlantic cable car- 
riers dominated by rival AT&T. What the Federal Telecommunications Laboratories had 
imagined, the Collins Radio Company, Cedar Rapids, Iowa, and the National Bureau of 
Standards CRPL, accomplished. 

On 28 October and 8 November 1951, Peter G. Sulzer and G. Franklin Montgomery, 
CRPL, and Irvin H. Gerks, Collins Radio, sent a continuous-wave 418-MHz (72-cm) radio 
signal from Cedar Rapids to Sterling, Virginia, via the Moon. On 8 November, a slowly 
hand-keyed telegraph message was sent over the circuit several times. The message was the 
same sent by Samuel Morse over the first U.S. public telegraph line: "What hath God 
wrought?" 67 

Unbeknownst to the CRPL/Collins team, the first use of the Moon as a relay in a 
communication circuit was achieved only a few days earlier by military researchers at the 
Naval Research Laboratory (NRL) . The Navy was interested in satellite communications, 
and the Moon offered itself as a free (if distant and rough) satellite in the years before an 
artificial satellite could be launched. In order to undertake lunar communication studies, 
the NRL built what was then the world's largest parabolic antenna in the summer of 1951. 
The dish covered over an entire acre (67 by 80 meters; 220 by 263 ft) and had been cut 
into the earth by road-building machinery at Stump Neck, Maryland. The one-megawatt 
transmitter operated at 198 MHz (1.5 meters). The NRL first used the Moon as a relay in 
a radio communication circuit on 21 October 1951. After sending the first voice trans- 
mission via the Moon on 24 July 1954, the NRL demonstrated transcontinental satellite 
teleprinter communication from Washington, DC, to San Diego, CA, at 301 MHz (1 
meter) on 29 November 1955 and transoceanic satellite communication, from 
Washington, DC, to Wahiawa, Oahu, Hawaii, on 23 January 1956. 68 

Later in 1956, the NRL's Radio Astronomy Branch started a radar program under 
Benjamin S. Yaplee to determine the feasibility of bouncing microwaves off the Moon and 
to accurately measure both the Moon's radius and the distances to different reflecting 
areas during the lunar libration cycle. Aside from the scientific value of that research, the 
information would help the Navy to determine relative positions on the Earth's surface. 
The first NRL radar contact with the Moon at a microwave frequency took place at 2860 
MHz (10-cm) and was accomplished with the Branch's 15-meter (50-ft) radio telescope. 69 

Although interest in bouncing radio and radar waves off the Moon drew military and 
civilian researchers to early radar astronomy conferences, lunar communication schemes 
failed to provide either a theoretical or a funding framework within which radar astrono- 
my could develop. The rapidly growing field of ionospheric research, on the other hand, 
provided both theoretical and financial support for radar experiments on meteors and 
the Moon. Despite the remarkable variety of radar experiments carried out in the years 
following World War II, radar achieved a wider and more permanent place in ionospher- 
ic research (especially meteors and auroras) than in astronomy. 



67. Grieg, Metzger, and Waer, pp. 652-663; "Via the Moon: Relay Station to Transoceanic 
Communication," Newsweek 27 (1 1 February 1946): 64; Sulzer, Montgomery, and Gerks, "An U-H-F Moon Relay," 
Proceedings of the IKE 40 ( 1952) : 361 . A few years later, three amateur radio operators, "hams" who enjoyed detect- 
ing long-distance transmissions (DXing), succeeded in bouncing 144-Mhz radio waves off the Moon, on 23 and 
27 January 1953. E. P. T, "Lunar DX on 144 Me!" QST37 (1953): 11-12 and 116. 

68. Gebhard, pp. 115-116; James H. Trexler, "Lunar Radio Echoes," Proceedings of the IRE 46 (1958): 
286-288. 

69. NRL, "The Space Science Division and E. O. Hulburt Center for Space Research, Program Review," 
1968, NRLHRC; Yaplee, R. H. Bruton, K. J. Craig, and Nancy G. Roman, "Radar Echoes from the Moon at a 
Wavelength of 10 cm," Proceedings oftheIRE46 (1958): 293-297; Gebhard, p. 118. 



26 TO SEE THE UNSEEN 



All that changed with the start of the U.S./U.S.S.R. Space Race and the announce- 
ment of the first planetary radar experiment in 1958. That experiment was made possible 
by the rivalries of the Cold War, which fostered a concentration of expertise and financial, 
personnel, and material resources that paralleled, and in many ways exceeded, that of 
World War II. The new Big Science of the Cold War and the Space Race, often indistin- 
guishable from each other, gave rise to the radar astronomy of planets. 

The Sputnik and Lunik missions were not just surprising demonstrations of Soviet 
achievements in science and technology. Those probes had been propelled off the Earth 
by ICBMs, and an ICBM capable of putting a dog in Earth-orbit or sending a probe to the 
Moon was equally capable of delivering a nuclear bomb from Moscow to New York City. 
Behind the Space Race lay the specter of the Cold War and World War III, or to para- 
phrase Clausewitz, the Space Race was the Cold War by other means. Just as the vulnera- 
bility of Britain to air attacks had led to the creation of the Chain Home radar warning 
network, the defenselessness of the United States against aircraft and ICBM attacks with 
nuclear bombs and warheads led to the creation of a network of defensive radars. The 
development of that network in turn provided the instrument with which planetary radar 
astronomy, driven by the availability of technology, would begin in the United States. 



Chapter Two 

Fickle Venus 



In 1958, MIT's Lincoln Laboratory announced that it had bounced radar waves off 
Venus. That apparent success was followed by another, but in England, during Venus' next 
inferior conjunction. In September 1959, investigators at Jodrell Bank announced that 
they had validated the 1958 results, yet Lincoln Laboratory failed to duplicate them. All 
uncertainty was swept aside, when the Jet Propulsion Laboratory (JPL) obtained the first 
unambiguous detection of echoes from Venus in 1961. 

As we saw in the case of radar studies of meteors and the Moon in the 1940s and 
1950s, planetary radar astronomy was driven by technology. The availability of military 
apparatus made possible the rise of radar astronomy in Britain in the 1940s. Just as the 
threat of airborne invasion gave rise to the Chain Home radar, the Cold War and its sci- 
entific counterpart, the Space Race, demanded the creation of a new generation of defen- 
sive radars, and those radars made possible the first planetary radar experiments. Even 
British and Soviet planetary radar astronomy were not free of the sway of military and 
space efforts. Thus, the Big Science efforts brought into being by the Cold War and the 
Space Race provided the material resources necessary for the emergence of planetary 
radar astronomy. 

The initial radar detections of Venus signaled a benchmark in radar capacity that 
separated a new generation of radars from their predecessors. High-speed digital com- 
puters linked to more powerful transmitters and more sensitive receivers utilizing state-of- 
the-art masers and parametric amplifiers provided the new capacity. As we saw in Chapter 
One, initial radar astronomy targets were either ionospheric phenomena, like meteors 
and auroras, or the Moon, whose mean distance from Earth is about 384,000 kilometers. 
The new radars reached beyond the Moon to Venus, about 42 million kilometers distant 
at its closest approach to Earth. 

Radar detections of the planets, while sterling technical achievements, were inca- 
pable of demonstrating the value of planetary radar as an ongoing scientific activity. As 
radar astronomy already had achieved with meteor studies, planetary radar became a sci- 
entific activity by solving problems left unsolved or unsatisfactorily solved by optical 
means. 

As they made their first detections of Venus, planetary radar astronomers found and 
solved two such problems. One was the rotation of Venus, the determination of which was 
prevented by the planet's optically impenetrable atmosphere. The other problem was the 
astronomical unit, the mean radius of the Earth's orbit around the Sun. Astronomers 
express the distances of the planets from the Sun in terms of the astronomical unit, but 
agreement on its exact value was lacking. Radar observations of Venus provided an exact 
value, which the International Astronomical Union adopted, and revealed the planet's 
retrograde rotation. 

While the astronomical unit and the rotation of Venus interested astronomers, they 
also held potential benefit for the nascent space program. In many respects, the problems 
solved by the first planetary radar experiments needed solutions because of the Space 
Race. By February 1958, when Lincoln Laboratory first tried to bounce radar waves off 
Venus, Sputnik 1 and the Earth-orbiting dog Laika were yesterday's news. The Space Race 
was hot, and so was the competition between the United States and the Soviet Union. 



27 



28 TO SEE THE UNSEEN 



Planetary radar astronomy rode the cresting waves of Big Science (the Space Race) and 
the Cold War well into the 1970s. 

From the Rad Lab to Millstone Hill 

Scientists and engineers at MIT's Lincoln Laboratory attempted to reach Venus by 
radar in 1958, because they had access to a radar of unprecedented capability. The radar 
existed because MIT, as it had since the days of the Radiation Laboratory, conducted mil- 
itary electronics research. Lincoln Laboratory did not emerge directly from the Radiation 
Laboratory but through its direct descendant, the Research Laboratory of Electronics 
(RLE). 

The RLE, a joint laboratory of the Physics and Electrical Engineering Departments, 
continued much of the fundamental electronic research of the Radiation Laboratory. The 
Signal Corps, Air Force, and the Office of Naval Research jointly funded the new labora- 
tory, with the Signal Corps overseeing the arrangement. Former Radiation Laboratory 
employees filled research positions at the RLE, which occupied a temporary structure on 
the MIT campus erected earlier for the Radiation Laboratory. The two leaders of the 
Lincoln Laboratory Venus radar experiment, Robert Price and Paul E. Green, Jr., were 
both student employees of the RLE. Price also had an Industrial Fellowship in Electronics 
from Sperry. Among the other early RLE fellowship sponsors were the General Radio 
Company, RCA, ITT, and the Socony-Vacuum Oil Company. 

In September 1949, the Soviet Union detonated its first nuclear bomb; within 
months civil war exploded in Korea. The need for a United States air defense capable of 
coping with a nuclear attack was urgent. Project Charles, a group of military and civilian 
experts, studied the problems of air defense. Its findings led directly to the creation of 
Lincoln Laboratory in the Autumn of 195 1. 1 

MIT was, in the words of Hoyt S. Vandenberg, U.S. Air Force chief of staff, "unique- 
ly qualified to serve as contractor to the Air Force for the establishment of the proposed 
[Lincoln] laboratory. Its experience in managing the Radiation Laboratory of World War 
II, the participation in the work of ADSEC [Air Defense Systems Engineering Committee] 
by Professor [George E.] Valley and other members of the MIT staff, its proximity to 
AFCRL [Air Force Cambridge Research Laboratories] , and its demonstrated competence 
in this sort of activity have convinced us that we should be fortunate to secure the services 
of MIT in the present connection." 2 

Lincoln Laboratory was to design and develop what became known as SAGE (Semi- 
Automatic Ground Environment), a digital, integrated computerized North-American 
network of air defense. SAGE involved a diversity of applied research in digital computing 
and data processing, long-range radar, and digital communications. The Army, Navy, and 
Air Force jointly underwrote Lincoln Laboratory through an Air Force prime contract. 
The Air Force provided nearly 90 percent of the funding. In 1954, Lincoln Laboratory 
moved out of its Radiation Laboratory buildings on the MIT campus and into a newly con- 
structed facility at Hanscom Field, in Lexington, Massachusetts, next to the Air Force 
Cambridge Research Center. 



1. "President's Report Issue," MIT Bulletin vol. 82, no. 1 (1946): 133-136; ibid., vol. 83, no. 1 (1947): 
154-157; ibid., vol. 86, no. 1 (1950): 209; "Government Supported Research at MIT: An Historical Survey 
Beginning with World War II: The Origins of the Instrumentation and Lincoln Laboratories," May 1969, typed 
manuscript, pp. 15-19 and 30-31, MITA; George E. Valley, Jr., rough draft, untitled four page manuscript, 13 
October 1953, 6/135/AC 4, and MIT Review Panel on Special Laboratories, "Final Report," pp. 132-133, MITA. 
James R. Killian, Jr., The Education of a College President: A Memoir (Cambridge: The MIT Press, 1985), pp. 71-76, 
recounts the founding of Lincoln Laboratory, too. 

2. Vandenberg to James R. Killian, Jr., 15 December 1950, 3/136/AC 4, MITA. A portion of the quote 
also appears in Killian, p. 71. 



FICKLE VENUS 29 



Lincoln Laboratory quickly began work on the Distant Early Warning (DEW) Line 
in the arctic region of North America. The first experimental DEW-line radar units were 
in place near Barter Island, Alaska, by the end of 1953. The radar antennas were enclosed 
by a special structure called a radome, which protected them from arctic winds and cold. 

Intercontinental Ballistic Missiles (ICBMs) challenged the DEW Line and the North 
American coordinated defense network, which had been designed to warn against air- 
plane attacks. ICBMs could carry nuclear warheads above the ionosphere, higher than any 
pilot could fly; existing warning radars were useless. In order to detect and track ICBMs, 
radars would have to recognize targets smaller than airplanes at altitudes several hundred 
kilometers above the Earth and at ranges of several thousand kilometers. The new radars 
would have to distinguish between targets and auroras, meteors, and other ionospheric 
disturbances, which experience already had shown were capable of crippling military 
communications and radars. 3 

In 1954, Lincoln Laboratory began initial studies of Anti-InterContinental Ballistic 
Missile (AICBM) systems and the creation of the Ballistic Missile Early Warning System 
(BMEWS). By the spring of 1956, the construction of an experimental prototype BMEWS 
radar was underway. Its location, atop Millstone Hill in Westford, Massachusetts, was well 
away from air routes and television transmitters and close to MIT and Lincoln Laboratory. 
The Air Force owned and financed the radar, while Lincoln Laboratory managed it under 
Air Force contract through the adjacent Air Force Cambridge Research Center. 

Herbert G. Weiss was in charge of designing and building Millstone. After graduat- 
ing from MIT in 1936 with a BS in electrical engineering, Weiss conducted microwave 
research for the Civil Aviation Authority in Indianapolis and worked in the MIT Radiation 
Laboratory. After the war, Weiss worked at Los Alamos, then at Raytheon, before return- 
ing to MIT to work on the DEW radars. 

Millstone embodied a new generation of radars capable of detecting smaller objects 
at farther ranges. Thanks to specially designed, 3-meter-tall (11-feet-tall) klystron tubes, 
Millstone was intended to have an unprecedented amount of peak transmitting power, 
1.25 megawatts from each klystron (2.5 megawatts total). Its frequency was 440 MHz (68 
cm) . The antenna, a steerable parabolic dish 26 meters (84-feet) from rim to rim, stood 
on a 27-meter-high (88-foot-high) tower of concrete and steel. Millstone began operating 
in October 1957, just in time to skin track the first Sputnik. 



3. Valley; "Final Report," pp. 133-137; "Government Supported," p. 33; C. L. Strong, Information 
Department, Western Electric Company, press release, 1 October 1953, 6/135/AC 4, MITA; Carl F. J. Overhage 
to LL Gen. Roscoe C. Wilson, 15 October 1959, and brochure, "Haystack Family Day, 10 October 1964," 
1/24/AC 134, MITA; F. W. Loomis to Killian, 17 April 1952, 4/135/AC 4, MITA; various documents in 
2/136/AC 4 and 7/135/AC 4, MITA; Overhage, "Reaching into Space with Radar," paper read at MIT Club of 
Rochester, 25 February 1960, pp. 6-7, 1 .1.1 A. For a popular introduction to the DEW Line, see Richard Morenus, 
Dew Line: Distant Early Warning, The Miracle of America 's First Line of Defense (New York: Rand McNally, 1957) . 



30 



TO SEE THE UNSEEN 




Figure 4 

The Lincoln Laboratory Millstone Hill Radar Observatory, ca. 1958. (Courtesy of MIT Lincoln Laboratory, Lexington, 
Massachusetts, photo no. P489-128.) 

Millstone furnished valuable scientific and technological information to the military, 
while advancing ionospheric and lunar radar research. In addition to testing and evaluat- 
ing new defense radar techniques and components, its scientific missions included mea- 
suring the ionosphere and its influence on radar signals (such as Faraday rotation), 
observing satellites and missiles, and performing radar studies of auroras, meteors, and 
the Moon, all of which were potential sources of false alarm for BMEWS radars. 4 

The Lunchtime Conversazione 

The idea of using the Millstone Hill radar to bounce signals off Venus arose during 
one of the customary lunchtime discussions between Bob Price and Paul Green. As MIT 
doctoral students and later as Lincoln Laboratory engineers, Price and Green worked 
closely together under Wilbur B. Davenport, Jr., their laboratory supervisor and disserta- 
tion director. They worked on different aspects of NOMAC (NOise Modulation And 
Correlation), a high-frequency communication system (known by the Army Signal Corps 
production name F9C) that used pseudonoise sequences, and on Rake, a receiver that 



4. Weiss 29 September 1993; "Final Report," pp. 136 and 138; Overhage, "Reaching into Space," p. 2; 
Overhage to Wilson, 30 June 1961, 1/24/AC 134, MITA; Allen S. Richmond, "Background Information on 
Millstone Hill Radar of MIT Lincoln Laboratory," 5 November 1958, typed manuscript, LLLA; Weiss, Space Radar 
Trackers and Radar Astronomy Systems, J A- 1740-22 (Lexington: Lincoln Laboratory, June 1961), pp. 21-23, 29, 44 
and 64; Price, "The Venus Radar Experiment," in E. D. Johann, ed., Data Handling Seminar, Aachen, Germany, 
September 21, 1959 (London: Pergamon Press, 1960), p. 81; Price, P. Green, Thomas J. Goblick, Jr., Robert H. 
Kingston, Leon G. Kraft, Jr., Gordon H. Pettengill, Roland Silver, William B. Smith, "Radar Echoes from Venus," 
Science 129 (1959): 753; "Missile Radar Probes Arctic," Electronics 30 (1957): 19; Pettengill 28 September 1993. 



FICKLE VENUS 31 



solved NOMAC multipath propagation problems. Later, what Lincoln Laboratory called 
NOMAC came to be called spread spectrum. 

Their work was vital to maintaining military communications in the face of enemy 
jamming. One of their units went to Berlin in 1959 in anticipation of a blockade to pro- 
vide essential communications in case of jamming. The Soviet Union already had demon- 
strated its jamming expertise against the Voice of America. Conceivably, all NATO com- 
munications could be jammed in time of war. The Lincoln Laboratory anti-jamming pro- 
ject was a direct response to that threat. 5 

Radio astronomy, which influenced the rise of planetary radar astronomy during the 
1960s, played a small role in the Lincoln Laboratory Venus experiment. Price actually had 
worked at the University of Sydney under radio astronomer Gordon Stanley and met such 
pioneers as Pawsey, Taffy Bowen, Paul Wild, Bernie Mills, and Chris Christiansen. A 
recently published book on radio astronomy by the Australian scientists J. L. Pawsey and 
Ronald N. Bracewell was the subject of lunch conversation between Green and Price in 
the Lincoln Laboratory cafeteria. The chapter on radar astronomy predicted that one day 
man would bounce radar waves off the planets. But radio astronomy did not give rise to 
the decision to attempt a radar detection of Venus. 6 

What did trigger the decision was the completion of the Millstone facility. Green and 
Price wondered if it was powerful enough to bounce radar signals off Venus. Gordon 
Pettengill, a junior member of the team, joined the lunchtime discussions. Trained in 
physics at MIT and an alumnus of Los Alamos, Pettengill had an office at Millstone. After 
making calculations on a paper napkin, though, they estimated that Millstone did not 
have enough detectability for the experiment, even if one assumed that Venus was per- 
fectly reflective. 

The lunchtime conversazione went nowhere, until Robert H. Kingston, who had a 
joint MIT and Lincoln Laboratory appointment, joined the discussions. Kingston had just 
built a maser. "Within an hour," Green recalled, "we had the whole damn thing mapped 
out." 7 The maser gave the radar receiver the sensitivity necessary to carry out the experi- 
ment. 

The maser, an acronym for Microwave Amplification by Stimulated Emission of 
Radiation, was a new type of solid-state microwave amplifying device vaunted by one 
author as "the greatest single technological step in radio physics for many years, with the 
possible exception of the transistor, comparable say with the development of the cavity 
magnetron during the Second World War." The maser was at the heart of the low-noise 
microwave amplifiers used in radio astronomy. The first radio-astronomy maser 
application, a joint effort by Columbia University and the Naval Research Laboratory, 
occurred in April 1958. The first use of a maser in radar astronomy, however, preceded 
that application by two months, in February 1958, at Millstone. While most masers 



5. William W. Ward, "The NOMAC and Rake Systems," The Lincoln Laboratory Journal vol. 5, no. 3 
(1992): 351-365; Green 20 September 1993; Price 27 September 1993. Green and Price acknowledged each 
other in their dissertations. Green, "Correlation Detection using Stored Signals" D.Sc. diss., MIT, 1953, and 
Price, "Statistical Theory Applied to Communication through Multipath Disturbances," D.Sc. diss., MIT, 1953. 

A history of the subject, R. A. Scholtz, The Origins of Spread-Spectrum Communications," IEEE 
Transactions on Communications COM-30 (1982): 822-854, is reproduced in Marvin K. Simon, Jim K. Omura, 
Scholtz, and Barry K. Levitt, eds., Spread Spectrum Communications (Rockville, Md.: Computer Science Press, Inc., 
1985), Volume 1, Chapter 2, "The Historical Origins of Spread-Spectrum Communications," pp. 39-134. Price, 
"Further Notes and Anecdotes on Spread-Spectrum Origins," IEEE Transactions on Communications COM-31 
(January 1983): 85-97, provides an absorbing anecdotal sequel to Scholtz. 

6. Pawsey and Bracewell, Radio Astronomy (Oxford: Clarendon Press, 1955) ; Green 20 September 1993; 
Price 27 September 1993. 

7. Green 20 September 1993; Pettengill 28 September 1993. For a description of the maser, see 
Kingston, A VHP Solid State Maser, Group Report M35-79 (Lexington: Lincoln Laboratory, 1957); and Kingston, 
A UHF Solid State Maser, Group Report M35-84A (Lexington: Lincoln Laboratory, 1958). 



32 TO SEE THE UNSEEN 



functioned above 1,000 MHz, Kingston's operated in the UHF region, around 440 MHz, 
and reduced overall system noise temperature to an impressive 170 K. 8 

Despite the maser's low noise level, Price and Green knew that they would have to 
raise the level of the Venus echoes above that of the noise. Their NOMAC antijamming 
work had prepared them for this problem. They chose to integrate the return pulses over 
time, as Zoltan Bay had done in 1946. In theory, the signals buried in the noise reinforced 
each other through addition, while the noise averaged out by reason of its random 
nature. 9 

A digital computer, as well as additional digital data processing equipment, linked to 
the Millstone radar system performed the integration and analysis of the Venusian echoes. 
An analog-to-digital converter, initially developed for ionospheric research by William B. 
Smith, digitized information on each radar echo. That information simultaneously was 
recorded on magnetic tape and fed to a solid-state digital computer. The experiment was 
innovative in digital-signal processing and marked one of the earliest uses of digital tape 
recorders. 10 

Venus or Bust 

Kingston's maser was installed at Millstone Hill just in time for the inferior conjunc- 
tion of Venus. However, a klystron failure left only 265 kilowatts of transmitter power avail- 
able for the experiment. On 10 and 12 February 1958, the radar was pointed to detect 
Venus, then some 45 million kilometers (28 million miles) away. The radar signals took 
about five minutes to travel the round-trip distance. In contrast, John DeWitt's signals 
went to the Moon and back to Fort Monmouth, NJ, in only about 2.5 seconds. 

Of the five runs made, only four of the digital recordings had few enough tape blem- 
ishes that they could be easily edited and run through the computer. Two of the four runs, 
one from each day, showed no evidence of radar returns. The others had one peak each. 
Price recalled, "When we saw the peaks, we felt very blessed." 11 It was not absolutely clear, 
however, that the two peaks were really echoes. 

Green explained: "We looked into our soul about whether we dared to go public with 
this news. Bob was the only guy who really stayed with it to the end. He had convinced 
himself that he had seen it, and he had convinced me that he had seen it. Management 
asked us to have a consultant look at our results, and we did." Thomas Gold of Cornell 
University looked at the peaks and said "Yes, I think you should publish this." Green and 
Price then published their findings in the 20 March 1959 issue of Science, the journal of 



8. J. V. Jelley, The Potentialities and Present Status of Masers and Parametric Amplifiers in Radio 
Astronomy," Proceedings of the IEEE 51 (1963): 31 and 36, esp. 30; J. W. Meyer, The Solid State Maser Principles, 
Applications, and Potential, Technical Report ESD-TR-68-261 (Lexington: Lincoln Laboratory, 1960), pp. 14-16; 
J. A. Giordmaine, L. E. Alsop, C. H. Mayer, and C. H. Townes, "A Maser Amplifier for Radio Astronomy at X- 
band," Proceedings of the IRE 47 (1959): 1062-1070; Pettengill and Price, "Radar Echoes from Venus and a New 
Determination of the Solar Parallax," Planetary and Space Science 5 (1961): 73. For Townes and the invention of 
the maser, see Paul Forman, "Inventing the Maser in Postwar America," Osiris ser. 2, vol. 7 (1992): 105-134. 

9. Price, p. 70; Price et al, p. 751. Later, Price acknowledged the pioneering integration work of Zoltan 
Bay in 1946. Price, p. 73. Kerr, "On the Possibility of Obtaining Radar Echoes from the Sun and Planets," 
Proceedings of the IRE 40 (1952): 660-666, specifically recommended long-period integration for radar observa- 
tion of Venus. 

10. Smith graduated MIT in 1955 with a master's degree in electrical engineering and worked with Price 
and Green on the F9C in Davenport's group. Smith 29 September 1993; Green 20 September 1993; Price 
27 September 1993; Price, p. 72; Price et al, p. 751; Scholtz, p. 838; Weiss, Space Radar Trackers, pp. 53, 59, 61 and 
63-64; "Biographical data, MIT Lincoln Laboratory," 18 March 1959, LLLA. 

11. Price 27 September 1993; Weiss, Space Radar Trackers, pp. 29 and 44; Price, pp. 71 and 76; Price et 
al, p. 751. 



FICKLE VENUS 33 



the American Association for the Advancement of Science, 13 months after their 
observations in February 1958. 12 

By then, despite the unsuccessful Lunik I Moon shot, the Soviet Union had achieved 
a number of successful satellite launches. The United States space effort still was marked 
by repeated failures. All of the four Pioneer Moon launches of 1958 ended in failure. 
There was a desperate need for good news; the Lincoln Laboratory publicity department 
gave the Venus radar experiment full treatment. In addition to a press conference, Green 
and Price quickly found themselves on national television and on the front page of the 
New York Times. President Eisenhower sent a special congratulatory telegram calling the 
experiment a "notable achievement in our peaceful ventures into outer space." 13 

Once Price and Green accepted the validity of the two peaks, the next step was to 
determine the distance the radar waves travelled to Venus and to calculate a value for the 
astronomical unit. They estimated a value of 149,467,000 kilometers and concluded, 
moreover, that it did not differ enough from those found in the astronomical literature to 
warrant a re-evaluation of the astronomical unit. 14 

The Lincoln Laboratory 1958 Venus experiment launched planetary radar astrono- 
my; Millstone Hill was the prototype planetary radar. Its digital electronics, recording of 
data on magnetic tape for subsequent analysis, use of a maser (or other low-noise 
microwave amplifier) and a digital computer, and long-period integration all became stan- 
dard equipment and practice. As with any experiment, scientists must be able to duplicate 
results. The next inferior conjunction provided an opportunity for scientists at Jodrell 
Bank to attempt Venus, too. 

Jodrell Bank had a new, 76-meter (250-ft) radio telescope, the largest of its type in 
the world. Although planned as early as 1951, the telescope did not detect its first radio 
waves until 1957 as a consequence of a long, nightmarish struggle with financial and con- 
struction difficulties. The civilian Department of Scientific and Industrial Research and 
the Nuffield Foundation underwrote its design and construction. Success in detecting 
Soviet and American rocket launches brought visits from Prince Philip and Princess 
Margaret and fame. Fame in turn brought solvency and a name (the Nuffield Radio 
Astronomy Laboratories, Jodrell Bank) . 

Although the design and construction of the large dish was unquestionably an enter- 
prise carried out with civilian funding, radar research at Jodrell Bank owed a debt to the 
United States armed forces; however, that military research was limited to meteor studies 
carried out with the smaller antennas, not the 76-meter (250-ft) dish. The U.S. Air Force 
and the Office of Naval Research supplied additional money for tracking rocket launch- 
es, while the European Office of the U.S. Air Force Research and Development Command 
(EOARDC) funded general electronics research at a modest level. During the Cuban mis- 
sile crisis, the 76-meter (250-ft) radio telescope served to detect missiles that might be 
launched from the Soviet Union. From intelligence sources, the locations of such missiles 
directed against London were known, and the telescope was aimed accordingly. No U.S. 
equipment or funding were engaged in this effort, though. 15 



12. Green 20 September 1993; Gold 14 December 1993; Price et al, pp. 751-753. 

13. Green 20 September 1993; Price 27 September 1993; Pettengill 28 September 1993; Overhage to 
Wilson, 24 March 1959, 1/24/AC 134, MITA; "Venus is Reached by Radar Signals," New York Times, vol. 108 (20 
March 1959), pp. 1 and 11. 

14. For their calculation of the astronomical unit, see Pettengill and Price, "Radar Echoes from Venus 
and a New Determination of the Solar Parallax," Planetary and Space Science 5 (1961): 71-74. 

15. Lovell, 11 January 1994; Lo\e\\,JodreU Bank, passim, but especially pp. 220-222, 224, 242, 225. On 
the Foundation, see Ronald William Clark, A Biography of the Nuffield Foundation (London: Longman, 1972). 
Created in 1962, EOARDC was essentially a military operation headquartered in Brussels. It underwrote a wide 
range of European scientific research, though more money went into electronics research than any other field. 
Howard J. Lewis, "How our Air Force Supports Basic Research in Europe," Science 131 (1960): 15-20. From 



34 



TO SEE THE UNSEEN 




Figure 5 

TheJodreU Bank 250-foot (76-meter) telescope in June 1961. The control room is partially visible bottom left. The 1962 and 
1964Jodrell Bank Venus radar experiments were carried out using a U.S.-supplied continuous-wave radar mounted on this 
telescope. (Courtesy of the Director of the Nuffield Radio Astronomy Laboratories, Jodrell Bank.) 

Preparation for the 1959 Venus experiment began in 1957, as the dish was reaching 
completion. The telescope, however, was not yet ready for radar work. John Evans recog- 
nized that its transmitter power and operating frequency would have to be raised in order 
to achieve critical extra gain for the Venus experiment. The 100-MHz (3-meter), 10-kilo- 
watt Moon radar was not powerful enough. The University of Manchester Physics 
Department had developed a 400-MHz (75-cm), 100-kilowatt klystron. "It was a real 
kludge," Evans later recalled, "because it was basically a Physics Department experiment. 
It was continuously pumped; it sat on top of vacuum pumps, which required liquid nitro- 
gen for cooling." 16 

Lovell had the General Electric Company of Britain supply a modulator for the kly- 
stron. Evans was responsible for designing and building the rest of the equipment. As the 
1958 Venus inferior conjunction approached, "we simply were not ready, and Lovell was 
quite upset," Evans explained. Out of desperation, Evans employed the 100-MHz Moon 
radar enhanced with a computer integration scheme, but the equipment failed to detect 
echoes. When Lincoln Laboratory announced its success, Evans recalled, "We shrugged 
and felt we were beaten to the punch." 

The 1958 Jodrell Bank failure put all that much more pressure on Evans to produce 
results during the next inferior conjunction of September 1959. The transmitter was more 



August 1957, when Jodrell Bank began preliminary calibration measurements to August 1970, the telescope 
gathered results for 68,538 hours. Of those, 4,877 hours (7.1% of operational time) represented "miscellaneous 
use." Of that "miscellaneous use," 2,498 hours (3.6% of operational time) were directly concerned with the space 
programs of the United States and the Soviet Union. Lovell, Out of the Zenith: Jodrell Bank, 1 957-1 970 (New York: 
Harper & Row, 1973) , p. 2. 

16. Evans 9 September 1993. 



FICKLE VENUS 35 



or less ready. The klystron was mounted in one of the telescope towers. "It was a royal 
pain," Evans remembered, "because we had to take liquid nitrogen up the elevator and 
then a vertical ladder to get to this darn thing." As if that were not enough, a water pump 
burned up, and the connectors on the coaxial cable carrying power to the dish burned 
out every ten or fifteen minutes. While still struggling with the connector problem, Evans 
made several runs on Venus. 

Evans was a junior scientist, having just received his Ph.D. in 1957. He felt he was 
under great pressure to produce positive results. Lovell was anxious to know if they had 
found an echo; the Duke of Edinburgh was about to visit. Evans looked at his data, taken 
from the first few minutes of each run, when he thought the apparatus was working. He 
had what looked like a return, but it could have been noise. Evans decided, "Well, I think 
we have an echo." The Venus detection was announced in the 31 October 1959 issue of 
Nature. The Duke of Edinburgh visited Jodrell Bank on 11 November 1959; he received 
an explanation and a demonstration of the technique, using the Moon as a target. 

Despite the patchwork equipment, the 50-kilowatt, 408-MHz (74-cm) radar obtained 
a total of 58 and three quarters hours of useful operating data, before Venus passed 
beyond its range. As expected, none of the echoes were stronger than the receiver noise 
level; integration techniques increased the strength of the echoes. 17 The Jodrell Bank sig- 
nal processing equipment was rather limited in its ability to search. Without accurate 
range or Doppler correction information, Evans had to make assumptions; he chose the 
Lincoln Laboratory 1958 published value. Not surprisingly, the value Jodrell Bank derived 
for the astronomical unit agreed with that determined at Lincoln Laboratory. The Jodrell 
Bank confirmation of the Lincoln Laboratory results placed them on solid scientific 
ground, that is, until Lincoln Laboratory repeated the experiment 

Fickle Venus 

Bob Price and his fellow Lincoln Laboratory investigators were highly optimistic 
about verifying their 1958 results. Millstone now had a peak transmitter power of 500 kilo- 
watts, almost twice the 1958 level. In addition to using a higher pulse repetition rate, 
which improved signal detectability, Price's team replaced the maser with a parametric 
amplifier. Like the maser, the parametric amplifier was a solid-state microwave amplifier. 
Parametric amplifiers were simpler, smaller, cheaper, and lighter than masers, and they 
did not require cryogenic fluids to keep them cool. Although masers generally were less 
noisy, the Millstone parametric amplifier was, Pettengill and Price reported, "gratifyingly 
stable and reliable in its operation." 18 

Over a four-week period around the inferior conjunction of Venus, the Lincoln 
Laboratory team made two types of radar observations. On 66 runs, they recorded the 
echoes digitally for subsequent computer processing, as they had done in 1958. The sec- 
ond approach, used on 117 runs, involved initial analog processing in a series of elec- 
tronic circuits, followed by digitization and integration in real time by the site's comput- 
er. It was their first attempt at a real-time planetary detection by radar. Of all the runs, only 
one displayed a peak sufficiently above the noise level to be statistically significant. When 
subjected to detailed analysis, though, the peak turned out to be only noise. Price and 



17. Evans 9 September 1993; Jodrell Bank, Moon and Venus Radar Passive Satellite Observations: Technical 
(Final) Report, October 1958-December 1960, AFCRL Report 1129 (Macclesfield: Nuffield Radio Astronomy 
Laboratories, 1961), p. 22; Evans and G. N. Taylor, "Radio Echo Observations of Venus," Nature 184 (1959): 
1358-1359; Lovell, Out of the Zenith, p. 193. The noise figure was 4.6 db. The frequency of the lunar radar was 
lowered from 120 MHz to 100 MHz, when it was found to interfere with operations at nearby Manchester 
Airport. 

18. Pettengill and Price, p. 73. 



36 TO SEE THE UNSEEN 



Pettengill concluded that "none of the individual runs show strong evidence of Venus 
echoes." 19 

Jodrell Bank had corroborated the 1958 results; yet with an improved radar, Lincoln 
Laboratory could not confirm them. The disparity between the results was perplexing 
and bothersome. "It is difficult to explain the disparity between the results obtained at the 
two Venus conjunctions. Our current feeling," wrote Green and Pettengill, "is that the 
planet's reflectivity may be highly variable with time, and that the two successes in 1958 
were observations made on very favorable occasions." 20 

At the Jet Propulsion Laboratory (JPL), the Lincoln Laboratory and Jodrell Bank 
experiments were viewed with disbelief. As an internal report stated in 1961, "It is not 
known at the present time with certainty that a radio signal has ever been reflected from 
the surface of Venus and successfully detected." 21 JPL investigators intended to obtain the 
first unambiguous detection of radar echoes from the Venusian surface. 

The Jet Propulsion Laboratory 

JPL began modestly in Pasadena, California, in 1936 as the Guggenheim 
Aeronautical Laboratory, California Institute of Technology (GALCIT) , rocket project, 
led by Hungarian-born professor Theodore von Karman and financed by Harry 
Guggenheim. Starting in 1940, with backing from the Army Air Corps, the GALCIT group 
turned into a vital rocket research, development, and testing facility. A 1944 contract 
signed by GALCIT, the Army Air Force, and the California Institute of Technology 
(Caltech) transformed it into a large permanent laboratory called the Jet Propulsion 
Laboratory, whose major responsibility was research, development, and testing of missile 
technology, including the country's first tactical nuclear missiles, the Corporal and 
Sergeant, for the Army. 

JPL electronics arose out of the need for missile guidance and tracking systems. 
William Pickering, a Caltech electrical engineering professor with a Ph.D. in physics, 
became the director of JPL in 1954 and remained in that position until 1976. His special- 
ization was electronics, not propulsion. Under Pickering's aegis, electronics grew in 
prominence at JPL and came to the forefront in 1958, when JPL became a NASA labora- 
tory and started work on a worldwide, civilian satellite communications network known 
today as the Deep Space Network (DSN) , 22 

The communications network, known originally as the Deep Space Instrumentation 
Facility (DSIF), was the home of planetary radar at JPL. The three leaders of the Venus 
radar experiment were engineers involved in its design, Eberhardt Rechtin, Robertson 
Stevens, and Walter K. Victor. Rechtin, the architect of the DSIF, had a Ph.D. in electrical 
engineering from Caltech. He also was an inventor, with Richard Jaffe (also at JPL), of 
CODORAC (COded DOppler, Ranging, And Command), a radio communication system 



19. Pettengill and Price, p. 73; Green and Pettengill, "Exploring the Solar System by Radar," Sky and 
Telescope 20 (1960): 12-13; Jelley, pp. 30 and 35. During the 1959 Lincoln Laboratory Venus experiment, over 
150 runs were made, yet no echoes as strong as those of 1958 were observed. Overall system noise temperature 
rose from 170 Kelvins in 1958 to 185 Kelvins with the parametric amplifier. For a discussion of parametric ampli- 
fiers, see Karl Heinz Locherer, Parametric Electronics: An Introduction (New York: Springer-Verlag, 1981), 
pp. 276-286. 

20. Green and Pettengill, p. 13. 

21. JPL, Research Summary No. 36-7, Volume 1, for the period December 1, 1960 to February 1, 1961 (Pasadena: 
JPL, 1961), pp. 68 and 70. 

22. "Jet" was a broader term than rocket and avoided any stigma still attached to that word. Clayton R. 
Koppes,yPL and the American Space Program: A History of the Jet Propulsion Laboratory (New Haven: Yale University 
Press, 1982), pp. ix, 4-5, 10-17, 20, 38, 45 and 65. 



FICKLE VENUS 



37 



that detected and tracked narrow band signals in the presence of wideband noise. 
CODORAC, whose electronics in many ways resembled Lincoln Laboratory's NOMAC, 
became the basis for much of the DSIF's electronics. Bob Stevens had an M.S. in electri- 
cal engineering from the University of California at Berkeley, and Walt Victor, who assist- 
ed Rechtin in developing CODORAC, had a B.S. in mechanical engineering from the 
University of Texas. 

JPL located its share of the DSIF antennas in the Mojave Desert, about 160 kilometers 
from JPL, on the Fort Irwin firing range near Goldstone Dry Lake, where GALCIT earlier 
had tested Army rockets. 23 The two antennas on which JPL investigators performed their 
Venus experiment in 1961 were artifacts of the funding and research agendas of both the 
military and NASA. The first was a 26-meter-diameter (85-feet-diameter) dish named the 
HA-DEC antenna, because its axes were arranged to measure angles in terms of local hour 
angle (HA) and declination (DEC). JPL installed it at Goldstone during the second half of 
1958 to track and receive telemetry from the military's Pioneer probes. 24 




Figure 6 

JPL Goldstone 26-meter HA-DEC antenna erected in late 1958 to track and receive telemetry from the military's Pioneer probes. 
It was used with the 26-meter AZ-EL antenna to detect radar echoes from Venus in 1961. (Courtesy of Jet Propulsion 
Laboratory, photo no. 333-5968 AC.) 



23. Rechtin, telephone conversation with author, 13 September 1993; Stevens 14 September 1993; 
Nicholas A. Renzetti, ed., A History of the Deep Space Network from Inception to January 1, 1969, vol. 1, Technical 
Report 32-1533 (Pasadena: JPL, 1 September 1971), pp. 6-7 and 11; William R. Corliss, A History of the Deep Space 
Network, CR-151915 (Washington: NASA, 1976), pp. 3-4 and 16; Craig B. Waff, The Road to the Deep Space 
Network," IEEE Spectrum (April 1993): 53; Scholtz, pp. 841-843; additional background material supplied from 
oral history collection, JPLA. 

24. Dish diameters have been expressed in meters only recendy. Initially, they were measured in feet. 
For the sake of consistency, diameters are given in both feet and meters diroughout the text. Victor, "General 
System Description," p. 6 in Victor, Stevens, and Solomon W. Golomb, eds., Radar Exploration of Venus: Goldstone 
Observatory Report for March-May 1961, Technical Report No. 32-132 (Pasadena: JPL, 1961); Corliss, Deep Space 
Network, pp. 16-17 and 20-25. 



38 



TO SEE THE UNSEEN 



JPL erected the second antenna for Project Echo. Echo, a large balloon in Earth 
orbit, tested the feasibility of long-range satellite communications. As such, it was heir to 
the lunar-repeater communication tests discussed in Chapter One. Originally funded by 
NASA's predecessor, the National Advisory Committee for Aeronautics (NACA) , and the 
Defense Department's space research organization, the Advanced Research Projects 
Agency (ARPA) , Project Echo became a JPL, NASA, and Bell Telephone Laboratories 
undertaking in an agreement signed in January 1959. 

The Echo experiments used the existing HA-DEC antenna to receive as part of a 
satellite circuit running from east to west. The west-to-east circuit, however, required the 
construction of an antenna capable of transmitting. Therefore, JPL installed a second 26- 
meter-diameter (85-feet-diameter) dish at Goldstone about a year after the HA-DEC 
antenna for Project Echo. The axes of the second antenna measured angles in terms of 
azimuth (AZ) and elevation (EL) ; hence, it was referred to as the AZ-EL antenna. 25 




Figure 7 

Jet Propulsion Laboratory Goldstone 26-meter AZ-EL antenna built far Project Echo and used with the 26-meter HA-DEC 
antenna to detect echoes from Venus in 1961. (Courtesy of Jet Propulsion Laboratory, photo no. 332-168.) 



25. Victor, "General System Description," in Victor, Stevens, and Golomb, p. 6; Corliss, Deep Space 
Network, pp. 25-27; Donald C. Elder, III, "Out From Behind the Eight Ball: Echo I and the Emergence of the 
American Space Program, 1957-1960," Ph.D. diss., University of California at San Diego, 1989, passim. For a his- 
tory of ARPA, see Richard J. Barber Associates, Inc., The Advanced Research Projects Agency, 1958-1974 
(Washington, D.C.: National Technical Information Service, 1975). For the story of JPL and Project Echo, see 
Stevens and Victor, eds., The Goldstone Station Communications and Tracking System for Project Echo, Technical Report 
32-59 (Pasadena: JPL, 1960); Victor and Stevens, "The Role of the Jet Propulsion Laboratory in Project Echo," 
IRE Transactions on Space Electronics and Telemetry SET-7 (1961): 20-28. 



FICKLE VENUS 39 



By August 1960, as Goldstone prepared to participate in Project Echo, the Lincoln 
Laboratory and Jodrell Bank Venus experiments already had taken place. Solomon 
Golomb, assistant chief of the Communications System Research Section under Walt 
Victor, asked his employee, Richard Goldstein, to design a space experiment to feed the 
rivalry between Eb Rechtin, JPL program director for the DSIF, and Al Hibbs, who was in 
charge of space science at JPL. Goldstein suggested the Venus radar experiment. Victor, 
JPL project engineer for the Echo program and recently promoted to chief of the 
Communications System Research Section, and Bob Stevens, head of the Communica- 
tions Elements Research Section, became the project managers. 26 

Rechtin, Victor, and Stevens organized the Venus experiment as a drill of the DSIF 
and its technical staff. The functional, organizational, and budgetary status of planetary 
radar astronomy as a test of the DSIF originated in their conception of the 1961 Venus 
experiment and defined planetary radar at JPL for over two decades. At the time, the lab- 
oratory was preparing for the first Mariner missions. Consequently, as Rechtin pointed 
out, JPL had "a particular interest in an accurate determination of the distance to Venus 
in order that we might guide our space probes to that target." 27 

The NASA Office of Space Science approved the Mariner 1 and 2 missions in July 
1960. Goldstone was to provide communications with them. The task would be more chal- 
lenging than communicating with a Ranger Moon probe. While a Ranger mission 
required three days, the Mariner missions would involve months of round-the-clock, high- 
level technical performance. In June 1960, even before final approval of the Mariner 
probes, Rechtin proposed the radar experiment to NASA, emphasizing not its scientific 
value, but the "practical, purely project point of view." 28 

In order to perform the Venus experiment, JPL had to modify the Echo equipment. 
Venus was a much farther object than the Earth-orbiting Echo balloon, and both differed 
radically as radar targets. Victor and Stevens, moreover, wanted to avoid long-term inte- 
gration and after-the-fact data reduction and analysis, that is, the Lincoln Laboratory and 
Jodrell Bank approach. Instead, JPL attempted a real-time radar detection of Venus. 

The JPL antennas were unlike those of Lincoln Laboratory and Jodrell Bank in many 
ways. They operated in tandem, the AZ-EL transmitting and the HA-DEC receiving. This 
bistatic mode, as it is called, offered advantages over the Millstone and Jodrell Bank mono- 
static mode, in which a single instrument both sent and received. Monostatic radars have 
to stop transmitting half the time in order to receive, while bistatic radars can operate con- 
tinuously, gathering twice the data in the same period of time. The Goldstone radars also 
operated at a higher frequency (S-band v. UHF) and sent a continuous wave, whereas the 
Lincoln Laboratory and Jodrell Bank radars transmitted discrete pulses. 

JPL also boosted the transmitting power and receiver sensitivity of the two radars. 
The normal output of the AZ-EL transmitter klystron tube was 10 kilowatts at 2388 MHz 
(12.6 cm), but engineers coaxed a nominal average power output of 13 kilowatts out of it. 



26. Golomb, The First Touch of Venus," paper presented at the Symposium Celebrating the Thirtieth 
Anniversary of Planetary Radar Astronomy, Pasadena, October 1991, Renzetti materials; Goldstein 7 April 1993; 
Goldstein 14 September 1993; Goldstein 19 September 1991; Stevens 14 September 1993; biographical materi- 
al and JPL Press Release, 23 May 1961, 3-15, Historical File, JPLA. 

27. Rechtin, "Informal Remarks on the Venus Radar Experiment," in Armin J. Deutsch and Wolfgang 
B. Klemperer, eds., Space Age Astronomy (New York: Academic Press, 1962), p. 365; Golomb, "Introduction," in 
Victor, Stevens, and Golomb, pp. 1-2; Rechtin, telephone conversation, 13 September 1993; Goldstein 
19 September 1991. 

28. Golomb, "Introduction," p. 1; JPL, Research Summary No. 36-7, p. 70; Rechtin, telephone conversa- 
tion, 13 September 1993; Waff, "A History of the Deep Space Network," manuscript furnished to author, 
ch. 6, pp. 22 and 24. Because the manuscript is not paginated sequentially, both chapter and page references are 
provided. 



40 TO SEE THE UNSEEN 



Raising the sensitivity of the HA-DEC receiver was a daunting challenge; the total receiv- 
er system noise temperature on Project Echo had been 1570 K! 29 

The technical solution was a maser and a parametric amplifier in tandem on the HA- 
DEC antenna. Charles T. Stelzried and Takoshi Sato created a 2388-MHz maser specifi- 
cally for the Venus radar experiment and suitable for Goldstone's tough desert ambient 
temperatures (from -12 to 43C; 10 to 110F) and climate (rain, dust, and snow). The 
maser and 2388-MHz parametric amplifier combined gave an overall average system noise 
temperature of about 64 K during the two months of the Venus experiment, considerably 
lower than the best achieved at Millstone in 1958 (170 K). As Victor and Stevens pro- 
claimed, 'This is believed to be the most sensitive operational receiving system in the 
world. "30 

"No Echo, No Thesis" 

Besides testing the personnel and materiel of the Goldstone facility, the JPL Venus 
experiment also was the doctoral thesis topic of two employees in Walt Victor's section, 
Duane Muhleman and Richard Goldstein. Muhleman graduated from the University of 
Toledo with a BS in physics in 1953, then worked two years at the NACA Edwards Air Force 
Base High-Speed Flight Station as an aeronautical research engineer, before joining JPL. 
As part of his duties at JPL, Muhleman tested the Venus radar system and its components 
during January, February, and March 1961, using the Moon as a target. For the Venus 
experiment, Muhleman contributed an instrument to measure Doppler spreading. 31 

Goldstein was a Caltech graduate student in electrical engineering. His task on the 
Venus radar experiment was to build a spectrum measuring instrument. It recorded what 
the spectrum looked like during reception of an echo and what it looked like when the 
receiver saw only noise. JPL hired his brother, Samuel Goldstein, a JPL alumnus and radio 
astronomer at Harvard College Observatory, as a consultant on the Venus experiment; 
Samuel also helped his brother with some of the radio techniques. 

Dick Goldstein wanted to use the Venus radar experiment as his thesis topic at 
Caltech, but his advisor, Hardy Martel, was highly skeptical. The inability of Lincoln 
Laboratory to detect Venus was widely known. Although he thought the task indisputably 
impossible, Martel finally agreed to accept the topic, but with a firm admonition: "No 
echo, no thesis." 32 



29. Rechtin, p. 366; Victor, "General System Description," pp. 6-7; Stevens and Victor, "Summary and 
Conclusions," p. 95; Victor and Stevens, "The 1961 JPL Venus Radar Experiment," IRE Transactions on Space 
Electronics and Telemetry SET-8 (1962): 85-90; Charles T. Stelzried, "System Capability and Critical Components: 
System Temperature Results," in Victor, Stevens, and Golomb, pp. 28-29. For a general description of the radar 
system, see M. H. Brockman, Leonard R. Mailing, and H. R. Buchanan, "Venus Radar Experiment," in JPL, 
Research Summary No. 36-8, Volume 1, for the period February 1, 1961 to April 1, 1961 (Pasadena: JPL, 1961), 
pp. 65-73; Victor and Stevens, "Exploration of Venus by Radar," Science 134 (1961): 46. The Jodrell Bank trans- 
mitter had a peak power of 50 kilowatts; Millstone's peak power was 265 kilowatts in 1958 and 500 kilowatts in 
1959. However, comparing the peak power ratings of pulse and continuous-wave radars is the electronic equiva- 
lent of comparing apples and oranges. One must compare their average power outputs. 

30. Stevens and Victor, "Summary and Conclusions," p. 95; Sato, "System Capability and Critical 
Components: Maser Amplifier," in Victor, Stevens, and Golomb, p. 17; Stelzried, "System Capability and Critical 
Components: System Temperature Results," pp. 28-29; H. R. Buchanan, "System Capability and Critical 
Components: Parametric Amplifier," in Victor, Stevens, and Golomb, pp. 22-25; Walter H. Higa, A Maser System 
for Radar Astronomy, Technical Report 32-103 (Pasadena: JPL, 1961); Higa, "A Maser System for Radar 
Astronomy," in K. Endresen, Low Noise Electronics (New York: Pergamon Press, 1962), pp. 296-304. 

31. Muhleman 8 April 1993; Muhleman 19 May 1994; Muhleman 27 May 1994; Goldstein 19 September 
1991; Stevens 14 September 1993; Golomb, "Introduction," p. 3; Stevens, "Additional Experiments: Resume," in 
Victor, Stevens, and Golomb, p. 70. Muhleman 's dissertation was "Radar Investigations of Venus," Ph.D. diss., 
Harvard University, 1963. 

32. Goldstein 7 April 1993; Goldstein 19 September 1991; Goldstein 14 September 1993. 



FICKLE VENUS 41 



On 10 March 1961, a month before inferior conjunction, the Goldstone radars were 
pointed at Venus. The first signals completed the round-trip of 113 million kilometers in 
about six and a half minutes. During the 68 seconds of electronic signal integration time, 
1 of 7 recording styluses on Goldstein's instrument deviated significantly from its zero 
level and remained at the new level. 

To verify that the deflection came from Venus and was not leakage from the trans- 
mitter or an instability in the receiver, the transmitter antenna was deliberately allowed to 
drift off target. Six and a half minutes later, the recording stylus on Goldstein's instrument 
returned to its zero setting. The experiment was immediately repeated with the same 
result. JPL had achieved the first real-time detection of a radar signal from Venus. And 
Dick Goldstein had his dissertation topic. 33 

On 16 March, Eb Rechtin telexed Paul Green: "HAVE BEEN OBTAINING REAL 
TIME RADAR REFLECTED SIGNALS FROM VENUS SINCE MARCH 10 USING 10 KW 
CW AT 2388 MC AT A SYSTEM TEMPERATURE OF 55 DEGREES." The following day, 
Green, John Evans (then at Lincoln Laboratory), Pettengill, and Price telexed back: 
"HEARTIEST CONGRATULATIONS ON YOUR SUCCESS WITH THE FICKLE LADY. 
MILLSTONE IS ON WITH THE USUAL MODE OF OPERATION BUT HAS HAD NO 
SUCH LUCK AS YET. PRESENT PARAMETERS 2.4 MEGAWATTS PEAK FOR 2 MIL- 
LISECONDS EVERY 33 MILLISECONDS 190 DEGREES KELVIN. " 3 * 

Following the initial contact, JPL conducted additional radar experiments almost 
daily from 10 March to 10 May 1961, collecting 238 hours of recorded radar data about 
Venus. 35 No previous Venus radar experiment, nor any others carried out in 1961, 
collected as many hours of data as the JPL experiment. 

The JPL experiment succeeded, because it did not depend on knowing the range to 
Venus, specifically; it did not depend on prior knowledge of the precise value of the astro- 
nomical unit. On the other hand, Lincoln Laboratory, as well as Jodrell Bank, had based 
its experiment on an assumed, yet commonly accepted, value for the astronomical unit, 
and, consequently, for the distance between Earth and Venus during inferior conjunction. 

"We Were Wrong." 

The results obtained by Lincoln and other laboratories in 1961 agreed with those 
obtained by JPL. That agreement led Gordon Pettengill to discern the error of the 1958 
Lincoln Laboratory observations. "In view of the generally excellent agreement among 
the various observations made at several wavelengths [in 1961]," Pettengill and his col- 
leagues concluded, "it seems likely that the results reported from observations of the 1958 
inferior conjunction are in error, although no explanation has been found." 36 

Green recalled: "It was sort of devastating, when the next conjunction of Venus came 
around, and we learned that we were wrong. We had the wrong value of the astronomical 
unit. It wasn't over here; it was way over there someplace. In fact, it wasn't even easy to go 
back and look at the original data and conclude that it was really over there. The original 



33. JPL Press Release, 23 May 1961, 3-15, Historical File, JPLA; Mailing and Golomb, "Radar 
Measurements of the Planet Venus," Journal of the British Institution of Radio Engineers 22 (1961): 298; Victor and 
Stevens, The 1961 JPL Venus Radar Experiment," IRE Transactions on Space Electronics and Telemetry SET-8 ( 1962) : 
90-91. Goldstein's dissertation was "Radar Exploration of Venus," Ph.D. diss., California Institute of Technology, 

34. 3-15, Historical File, JPLA. 

35. Victor and Stevens, "1961 JPL Venus Radar Experiment," p. 91. 

36. Pettengill, Briscoe, Evans, Gehrels, Hyde, Kraft, Price, and Smith, "A Radar Investigation of Venus," 
The Astronomical Journal 67 (1962): 186. 



42 TO SEE THE UNSEEN 



data just had turned out to be too noisy.. ..It was a chastening experience for us." 37 Price 
remembered someone entering his office with "a rather long look on his face" and saying, 
"Bob, I think we've been found to be wrong." It was an embarrassing moment. 

Price re-examined the Lincoln Laboratory 1958 tapes. "I wanted to be sure that we 
hadn't detected it. I really mean that. I wanted to make sure that we had a negative result 
and that by accident we didn't have two wrongs making a right, that is, false processing of 
the 1958 data led to a false result, so the proper processing of the 1958 data would agree 
with JPL. I wanted to prove that that was not the case. So I went back and found the peaks, 
just as I had done before. I made a meticulous measurement of their position, which is the 
whole thing that the false echo hinged on. I developed with magnetic powder over and 
over again those tapes, and I inspected them until my eyes were sore. I reran the Fortran 
programs and checked all the programs, because you could create a timing error in the 
program." 

The experience reminded Price of his work in Australia. Every day, his group had 
made ink-pen recordings of the radio sky over the antenna, usually recording only ran- 
dom lines, but a peak appeared on two successive days. Did the peak mean a detection of 
deuterium? They decided that it was a fluke and published their negative results. "If we 
had behaved the same way at Millstone," Price reflected, "we might have saved ourselves 
some embarrassment. But that is hindsight." The two Venus pulses arrived 2.2 millisec- 
onds apart. "We just turned our back on it," Price admitted, "did a little wishful thinking, 
and said, 'That's the same pulse.'...! just pulled them together, ignored the 2.2-millisec- 
ond difference, and sat one on top of the other." 38 

Whatever the cause of the 1958 false readings, JPL was unquestionably the first to 
detect radar waves reflected off Venus. The literature contains two earlier, but after-the- 
fact detections. Only months after acknowledging JPL's priority, Lincoln Laboratory 
found on their data tapes a detection of Venus on 6 March 1961, a few days prior to that 
of JPL. Later, in 1963, Lincoln Laboratory electrical engineer Bill Smith re-examined the 
1959 data tapes and found that an echo had been recorded on 14 September 1959. 39 Such 
after-the-fact discoveries are not uncommon in the history of science, and radar 
astronomers from both JPL and MIT thirty years later commemorated JPL's uncon tested 
priority in detecting radar waves reflected off Venus. 

Once JPL unambiguously detected echoes from Venus, the key question planetary 
radar astronomers addressed was the size of the astronomical unit. In order to determine 
more precisely the Earth-to-Venus distance, JPL ran ranging experiments between 18 
April and 5 May 1961. In the July 1961 issue of Science, Victor and Stevens announced a 
preliminary value for the astronomical unit of 149,599,000 kilometers with an accuracy of 
1500 kilometers. 40 That value was over 100,000 kilometers larger than the false radar 
value determined by Lincoln Laboratory in 1958 and confirmed by Jodrell Bank in 1959, 
149,467,000 kilometers. Values obtained from preliminary analyses of radar data at 
Lincoln Laboratory and elsewhere in 1961 agreed closely with that of JPL (Table 1). 

When Lincoln Laboratory undertook its 1961 Venus radar experiment, Gordon 
Pettengill, joined by John Evans, took over Bob Price's leadership role. Evans had left 
Jodrell Bank for Lincoln Laboratory during the previous summer, after being courted by 
the National Bureau of Standards and Stanford. At Jodrell Bank, Evans had had one 



37. Green 20 September 1993. 

38. Price 27 September 1993. 

39. Smith 29 September 1993; Smith, "Radar Observations of Venus, 1961 and 1959," The Astronomical 
Journal 68 (1963): 17; Pettengill et al, "A Radar Investigation of Venus," p. 183. 

40. Rechtin, p. 367; Victor, "General System Description," p. 7; Victor and Stevens, "1961 JPL Venus 
Radar Experiment," p. 88; Victor and Stevens, "Exploration of Venus by Radar," p. 46. 



FICKLE VENUS 



43 



Table 1 


Radar Values for the Astronomical Unit, 1961-1964 






Error of 


Value of 








Measurement 


Astronomical Unit 








(in kilometers) 


(in kilometers) 






Optical Values 










Spencer Jones 


17,000 


149,675,000 






Eugene Rabe 


10,000 


149,530,000 






1961 Conjunction 










Jet Propulsion Laboratory 










July 1961 (1) 


1,500 


149,599,000 






August 1961 (2) 


500 


149,598,500 






Muhleman (3) 


250 


149,598,845 






Lincoln Laboratory 










May 1961 (4) 


1,500 


149,597,700 






Corrected value (5) 


400 


149,597,850 






Jodrell Bank (6) 


5,000 


149,601,000 






RCA/Flower and Cook Observatory (7) 


200 


149,596,000 






Soviet Union 










Pravda value (8) 


130,OOOP 


149,457,000 






November 1961 (9) 


3,300 


149,598,000 






Revised Value (10) 


2,000 


149,599,300 






Space Technology Laboratories (11) 


13,700 


149,544,360 






1962 Conjunction 










Jodrell Bank (12) 


900 


149,596,600 






Soviet Union (13) 


270 


149,597,900 






Jet Propulsion Laboratory Muhleman (14) 


670 


149,598,900 






1964 Conjunction 










Lincoln Laboratory (15) 


100 


149,598,000 






Jet Propulsion Laboratory (16) 


100 


149,598,000 






Soviet Union (17) 


400 


149,598,000 






IAU Value 




149,600,000 






Sources 






1. W.K. Victor and R. Stevens, "Exploration of Venus by Radar," Science 134 (July 1961): 46-48. 






2. D.O. Muhleman, D.B. Holdridge, and N. Block, "Determination of the Astronomical Unit from Velocity, Ranee, 
and Integrated Velocity Data, and the Venus-Earth Ephemeris," pp. 83-92 in W.K. Victor, R. Stevens, and S.W. Golomb, eds., 






Raiitir Exploration of Venus: Goldstar* Observatory Report jar March-May 1961, Technical Report 32-132 (Pasadena: Jet Propulsion 






Laboratory, 1 August 1961). 






3. D.O. Muhleman, D.B. Holdridge, and N. Block, The Astronomical Unit Determined by Radar Reflections from 
Venus," The Astronomical Joumal67 (1962): 191-203. 






4. Staff, Millstone Radar Observatory. Lincoln Laboratory, 'The Scale of the Solar System," Nature 190 (13 May 1961): 






5. G.H. Pettengill, H.W. Briscoe, J.V. Evans, E. Gehrels, G.M. Hyde, L.G. Kraft, R. Price, and W.B. Smith, "A Radar 






Investigation of Venus," The Astronomical foumal&l (1962): 181-190. 






6. J.H. Thomson, J.E.B. Ponsonby, G.N. Taylor, and R.S. Roger, "A New Determination of the Solar Parallax by Means 
of Radar Echoes from Venus," Mi/urel90 (1961): 519-520. 






7. I. Maron, G. Luchak, and W. Bliustein, "Radar Observation of Venus," Science 134 (1961): 1419-1421. 






8. VA. Kotelnikov, "Radar Contact with Venus," Journal of the British Institution of Radio Engineers 22 ( 1961 ) : 293-295. 
9. VA. Kotelnikov, V.M. Dubrovin, VA. Morozov, G.M. Petrov, O.N. Rzhiga, Z.G. Trunova, and A.M. Shakhovoskoy, 






"Results of Radar Contact with Venus in 1961," Radio Engineering and Electronics Physics 11 (November 1961): 1722-1733. 
10. Vj\. Kotelnikov, B A. Dubmskiy, M.D. Kislik, and D.M. Tsvetkov, "Refinement of the Astronomical Unit on the Basis 
of the Results of Radar Observations of the Planet Venus in 1961," NASA TT F-8532, October 1963. 






11. J.B. McGuire, E.R. Spangler, and L. Wong, "The Size of the Solar System," Scientific American vol. 204, no. 4 (1961 ): 






64-72. 






12. J.E.B. Ponsonby, I. H. Thomson, and K.S. Imrie, "Radar Observations of Venus and a Determination of the 






Astronomical Unit," Monthly Notices of the Royal Astronomical Society 128 (1964): 1-17. 
13. V.A. Kotelnikov, V.M. Dubrovin, VA. Dubinskii, M.D. Kislik, B.I. Kusnctsov, I.V. Lishin. VA. Morosov, G.M. Petrov, 






O.N. Rzhiga, GA. Sytsko, and A.M. Shakhovskoi, "Radar Observations of Venus in the Soviet Union in 1962," Soviet Physia- 






DoUady 8 (1964): 642-645. 






14. D.O. Muhleman, Relationship Between the system of Astrcmomical Constants and the Radar determinations of the Astronomical 
Unit, Technical Report 32-477 (Pasadena: Jet Propulsion Laboratory, 15 January 1964). 






15. J.C. Pecker, ed.. Proceedings of the Twelfth General Assembly (New York: Academic Press, 1966), p. 602. 






16. J.C. Pecker, ed., Proceedings of the Twelfth General Assembly (New York: Academic Press, 1966), p. 603. 






17. VA. Kotelnikov, Yu. N. Alcksandrov, L.V. Apraksin, V.M. Dubrovin, M.D. Kislik, B.I. Kuznclsov, G.M. Petrov. O.N. 






Rzhiga, A.V. Franlsesson. and A.M. Shakhovskoi, "Radar Observations of Venus in the Soviet Union in 1964," Soviet Phyaa- 






DoUady 10 (1966): 578-580. 







44 TO SEE THE UNSEEN 



technical assistant; but at Lincoln Laboratory, as Bernard Lovell pointed out, he had "an 
army of engineers and technicians together with a transmitter vastly superior to the one 
at Jodrell Bank." 

Evans' departure from Jodrell Bank could not have come at a worse time, hi the 
opinion of Lovell. "For me it was the beginning of a distressing series of losses of the bril- 
liant young men who had been with me throughout the crisis of the telescope and whose 
devotion and skill had been a determining factor in the immediate success of the instru- 
ment. But who could expect a young man to resist a lavish red carpet reception and an 
offer of a salary many times greater than any sum which we could possibly offer him?" 41 

During the 1961 Venus experiment, the Millstone Hill radar ran at peak transmitting 
power, 2.5 megawatts. The increased transmitter power overcame the higher overall 
receiver noise temperature (240 K) to make the telescope a far more capable instrument. 
Pettengill and his colleagues aimed their radar at Venus on 6 March 1961, again using a 
technique to provide real-time detection. No echoes appeared until 24 March. 
Preliminary analysis yielded a value for the astronomical unit of 149,597,700 1,500 kilo- 
meters in May 1961. 42 That agreed closely with JPL's preliminary value, 149,599,000 kilo- 
meters. Despite considerable obstacles, and chastened by their 1959 false detection, 
Jodrell Bank investigators also found a value for the astronomical unit that agreed with the 
JPL value. 

In 1959, John H. Thomson took over the planetary radar program, and in the 
autumn of 1960, Lovell added John E. B. Ponsonby, who had come to Jodrell Bank to work 
on a doctorate after graduating in electrical engineering from Imperial College, London. 
Ponsonby had experience in meteor radar through his high school teacher and one-time 
member of the Jodrell Bank group, Ian C. Browne. 43 

Working from notes and memoranda left by Evans, the new team, which included G. 
N. Taylor and R. S. Roger, put together a radar system that "yielded a clear-cut and deci- 
sive answer after only a few 5 minute integration periods." 44 The first thing they did, how- 
ever, was to abandon the atrocious klystron. With most of the problems that plagued the 
1959 experiment overcome, with a more sensitive receiver, and with peak power output 
boosted from 50 to 60 kilowatts, the 76-meter (250-ft) Jodrell Bank telescope detected 
Venus beginning 8 April 1961, a few weeks after both JPL and Lincoln Laboratory had 
started their experiments, and ending 25 April 1961. 

Jodrell Bank calculated a value for the astronomical unit, 149,600,000 5000 kilo- 
meters, 45 close to the preliminary values of JPL (149,599,000 kilometers) and Lincoln 



41 . Lovell, Out of the Zenith, pp. 192 and 195; Evans 9 September 1993; Green 20 September 1993; Smith 
29 September 1993; Pettengill 28 September 1993. 

42. The Staff, Millstone Radar Observatory, Lincoln Laboratory, The Scale of the Solar System," Nature 
190 (1961): 592; Pettengill et al, "A Radar Investigation of Venus," pp. 182-183; Pettengill and Price, p. 73; 
Pettengill, "Radar Measurements of Venus," in Wolfgang Priester, ed., Space Research III, Proceedings of the Third 
International Space Science Symposium (New York: Interscience Publishers Division, John Wiley and Sons, 1963) , p. 
874; Overhage to Wilson, 22 May 1961, 1/24/AC 134, MITA. 

43. Ponsonby 1 1 January 1994; I. C. Browne and T. R. Kaiser, The Radio Echo from the Head of Meteor 
Trails, " Journal of Atmospheric and Terrestrial Physics 4 (1953): 14. 

44. Evans 9 September 1993; Lovell, Out of the Zenith, pp. 198-199; Thomson, Ponsonby, Taylor, and 
Roger, "A New Determination of the Solar Parallax by Means of Radar Echoes from Venus," Nature 190 (1961): 
519-520. The Jodrell Bank experiment was funded by Air Force contract no. AF61(052)-172. John Evans, then 
of Lincoln Laboratory, privately had communicated the laboratory's results to Thomson at Jodrell Bank. 

45. I have calculated this value from the information provided in Thomson, Ponsonby, Taylor, and 
Roger, pp. 519-520. While the authors concern themselves with the solar parallax, they also provide a figure for 
the light-time of the astronomical unit, 499,011 0.017 seconds, which represents the time taken by radar waves 
to travel the distance of one astronomical unit, and another for the speed of light, 299,792.5 kilometers per sec- 
ond, which is the same as the speed of electromagnetic waves. By multiplying the two figures, I obtained a prod- 
uct of 149,599,750 kilometers. 

The first published value of the astronomical unit I have found was in the comments given by Thomson 
following a presentation by Mailing and Golomb at a convention in Oxford that took place 5-8 July 1961. The 
date of publication was October 1961. Mailing and Golomb, p. 302. 



FICKLE VENUS 45 



Laboratory (149,597,700 kilometers), but with a far greater possible error of measure- 
ment. Similar results came from an unexpected source. RCA's Missile and Surface Radar 
Division in Moorestown, New Jersey, carried out its first and last planetary radar experi- 
ment in 1961. The Division performed radar research for the Army Signal Corps and the 
Navy, and in 1960, the Division performed solar radio experiments using a missile-track- 
ing radar. On their Venus radar experiment, RCA investigators collaborated with the 
Flower and Cook Observatory of the University of Pennsylvania. Between 12 March and 8 
April 1961, RCA tracked Venus with a BMEWS experimental radar in order to measure 
the astronomical unit. In over six hours of transmitted signals, they found only four peaks 
from which they calculated a value for the astronomical unit of 149,596,000 200 kilo- 
meters, 46 only 3,000 kilometers less than the JPL value. Not all Venus radar results agreed 
with those of JPL, however. 

In the Soviet Union, planetary radar was fundamental to the space program. One of 
the main objectives of the Crimean Venus experiment was to calculate a more precise 
value for the astronomical unit for use in launching planetary probes. The calculation of 
the orbit of the Mars-1 probe, in November 1962, utilized a radar-based value for the astro- 
nomical unit. The Institute of Radio Engineering and Electronics (IREE) of the U.S.S.R. 
Academy of Sciences, in association with other unnamed (but presumably military and 
intelligence) organizations and under the direction of Vladimir A. Kotelnikov, of the 
Soviet Academy of Sciences, designed and built planetary radar equipment that was 
installed at the Long-Distance Space Communication Center, located near Yevpatoriya in 
the Crimea. The IREE installation had nothing to do with the radar work carried out in 
the Soviet Union in 1946 on meteors or between 1954 and 1957 on the Moon. 

The IREE planetary radar was a monostatic pulse 700-MHz (43-cm) system. For the 
receiver, the IREE expressly designed both a parametric and a paramagnetic amplifier, 
another form of solid-state, low-noise microwave amplifier. The noise temperature of the 
entire receiver (without antenna) was claimed to be 20 10 K. The antenna was an array 
of eight 16-meter dishes, unlike any design ever used in the United States or Britain for 
planetary radar astronomy. 47 

Kotelnikov and his colleagues observed Venus between 18 and 26 April 1961. Their 
preliminary analysis of the data yielded an estimate of the astronomical unit, 149,457,000 
kilometers, which appeared in the newspapers Pravda and Izvestiia on 12 May 1961. Over 
100,000 kilometers less than the JPL and other values, the Soviet astronomical unit mea- 
surement was so incredibly incongruous, that Solomon Golomb told a conference of 
astronomers, "we should congratulate our Russian colleagues on the discovery of a new 



46. W. O. Mehuron, "Passive Radar Measurements at C-Band using the Sun as a Noise Source," The 
Microwave Journal 5 (April, 1962): 87-94; David K. Barton, "The Future of Pulse Radar for Missile and Space 
Range Instrumentation," IRE Transactions on Military Electronics MIL-5, no. 4 (October, 1961): 330-351; Irving 
Maron, George Luchak, and William Blitzstein, "Radar Observation of Venus," Science 134 (1961): 1419-1420. 

47. B. I. Kuznetsov and I. V. Lishin, "Radar Investigations of the Solar System Planets," in Air Force 
Systems Command, Radio Seventy Years (Wright-Patterson AFB, Ohio: Air Force Systems Command, 1967), 
pp. 187-188, 190 and 201; Vladimir A. Kotelnikov, "Radar Contact with Venus, "Journal of the British Institution of 
Radio Engineers 22 (1961): 293; Kotelnikov, L. V. Apraksin, V. O. Voytov, M. G. Golubtsov, V. M. Dubrovin, N. M. 
Zaytsev, E. B. Korenberg, V. P. Minashin, V. A. Morozov, N. I. Nikitskiy, G. M. Petrov, O. N. Rzhiga, and A. M. 
Shakhovskoy, "Radar System Employed during Radar Contact with Venus in 1961," Rndio Engineering and 
Electronic Physics II (1962): 1715-1716. For abrief history of the IREE, see Y.V. Gulyaev, "40 Years of the Institute 
of Radioengineering and Electronics of the Russian Academy of Sciences," Radiotekhnika Elektronika vol. 38, no. 
10 (October 1993): 1729-1733. Soviet investigators performed radar studies of meteors in 1946 and of the Moon 
in 1954-1957, according to A. E. Solomonovich, "The First Steps of Soviet Radio Astronomy," pp. 284-285 in 
Sullivan. Although radar astronomers recently have used the arrayed dishes of the Very Large Array in bistatic 
experiments, dish arrays have not been used as transmitting antennas. 



46 TO SEE THE UNSEEN 



planet. It surely wasn't Venus!" Retrospectively, Kotelnikov explained that "random real- 
izations of noise were taken for reflected signals." 48 

The cause of the Soviet error might have been rooted in Cold War competition, 
which placed Soviet scientists under great pressure to produce results quickly for political 
reasons. The Pravda and hvestiia announcements appeared on 12 May 1961, six days after 
the Jodrell Bank, but before the Lincoln Laboratory, announcements. If published 
sources had guided Kotelnikov and his colleagues, they would have been the erroneous 
Lincoln Laboratory and Jodrell Bank results of 1958 and 1959, with which the hvestiia 
value agreed closely (within 10,000 kilometers). 

The Cold War prevented communication and cooperation among planetary radar 
investigators. The Space Race in 1961 was still an extension of the Cold War; informal 
communications did not exist. Lincoln Laboratory did secret military research; JPL was a 
sensitive space research center with connections to ARPA, a military research agency. 
Jodrell Bank did not yet have ties with their Soviet counterparts. While Lincoln 
Laboratory, JPL, and Jodrell Bank personnel exchanged data, such informal links with 
Soviet scientists did not and could not exist. 

Kotelnikov and his associates at the IREE, after realizing their error, turned their 
attention to a complete analysis of the raw radar data recorded on magnetic tape with the 
help of a special analyzer. Their new value, 149,598,000 3300 kilometers, agreed closely 
with those of the United States and Britain. 49 Although the Soviet and British errors of 
measurement were greater than those of the American laboratories, they were far less 
than the values obtained by optical methods. The accuracy of the radar over the optical 
method and the general agreement among the preliminary results obtained in the United 
States, Britain, and the Soviet Union were the basis for a re-evaluation of the astronomi- 
cal unit by the International Astronomical Union (IAU) . 

Redefining the Astronomical Unit 

The re-evaluation of the astronomical unit was part of a general movement within 
the IAU to reform the entire system of astronomical constants conventionally used to com- 
pute ephemerides. On 21 August 1961, shortly after JPL, Lincoln Laboratory, and Jodrell 
Bank announced their first estimations of the astronomical unit, the IAU executive com- 
mittee decided to organize a symposium on the system of astronomical constants. That sys- 
tem rested upon observations made in the nineteenth century and values adopted at 
international conferences held in Paris in 1896 and 191 1. 50 

By 1950, two competing optical methods provided more accurate values for the astro- 
nomical unit. Harold Spencer Jones, Astronomer Royal of Great Britain from 1933 to 
1955, used a trigonometric approach based on the triangulation of Eros. The orbit of the 



48. Kotelnikov et al, "Radar System," pp. 1715 and 1721; Kotelnikov, "Radar Contact," p. 294; Mailing 
and Golomb, p. 300; Kotelnikov, "Radar Observations of the Planet Venus in the Soviet Union in April, 1961," 
typed manuscript, 27 February 1963, anonymous translation of a technical report of the Soviet Institute of Radio 
Engineering and Electronics, DTIC report number AD-401137, pp. 41-42, Renzetti materials. The Soviet publi- 
cation venue and aberrant astronomical unit value raise serious doubts about the veracity of their announce- 
ment. 

49. Kotelnikov et al, "Radar System," p. 1721; Kuznetsov and Lishin, p. 188; Kotelnikov, "Radar 
Observations," p. 2; Kotelnikov, Dubrovin, Morozov, Petrov, Rzhiga, Z. G. Trunova, and Shakhovoskoy, "Results 
of Radar Contact with Venus in 1961," Radio Engineering and Electronics Physics 11 (1962): 1722 and 1725. For a 
discussion of the integration technique, see V. I. Bunimovich and Morozov, "Small-Signal Reception by the 
Method of Binary Integration," ibid., pp. 1734-1740. 

50. Jean Kovalevsky, ed., The System of Astronomical Constants (Paris: Gauthier-Villars and Cie., 1965), p. 
1; Walter Fricke, "Arguments in Favor of the Revision of the Conventional System of Astronomical Constants," 
in J. C. Pecker, ed., Proceedings of the Twelfth General Assembly (New York: Academic Press, 1966), p. 604. 



FICKLE VENUS 47 



asteroid, discovered in 1898 by Berlin astronomer Gustav Witt, approaches Earth at regu- 
lar intervals. As president of the IAU Solar Parallax Commission, Spencer Jones oversaw 
a worldwide operation to record photographic observations of Eros during its closest 
approach to Earth in 1930 and 1931. Through a complicated analysis of nearly 3,000 pho- 
tographs, Spencer Jones estimated the astronomical unit to be 149,675,000 17,000 kilo- 
meters. Eugene Rabe, an astronomer at the Cincinnati Observatory, applied the so-called 
dynamic method to observations of Eros between 1926 and 1945. He took into account 
the gravitational effects of the Earth, Mars, Mercury, and Venus on the orbit of Eros, and 
arrived at a value of 149,530,000 10,000 kilometers. 51 

In addition, investigators at the Space Technology Laboratories (STL), a wholly- 
owned subsidiary of Ramo-Wooldridge (later TRW) , computed a value from data acquired 
during the Pioneer 5 mission. In figuring the probe's trajectory, STL chose Rabe's value 
over that of Lincoln Laboratory in 1958. Not surprisingly, STL found a value for the astro- 
nomical unit, 149,544,360 13,700 kilometers, in agreement with Rabe, but with a greater 
error of measurement. The STL value hardly challenged the more accurate ground-based 
radar measurements. Its "published accuracy," Walter Fricke, astronomer and professor at 
the Heidelberg Astronomisches Rechen-Institut, judged, "does not yet indicate any advan- 
tage over the traditional methods." 52 The Pioneer 5 value did not play any part in the 
lAU's revision of the astronomical unit. 

The organizing committee of the IAU symposium on astronomical constants 
brought together astronomers from the United States and Europe who were responsible 
for drawing up the ephemerides. COSPAR (the Committee on Space Research) named an 
ad hoc committee to participate in the symposium, and additional astronomers from the 
United States, Britain, France, West Germany, Portugal, the Soviet Union, and South 
Africa took part. The members of the organizing committee included Eb Rechtin, theJPL 
manager of the DSIF; Dirk Brouwer, director of the Yale Observatory; and Gerald M. 
Clemence, scientific director of the U.S. Naval Observatory in Washington. Both Brouwer 
and Clemence had helped JPL with the Venus radar experiment ephemerides. Among the 
additional astronomers participating in organizing committee activities were two radar 
astronomers, Dewey Muhleman and Irwin I. Shapiro. 53 

Soon after the 1961 Venus experiment, Muhleman left JPL for the Harvard 
Astronomy Department. There, under Fred Whipple, A. Edward Lilley, and William Liller, 
he completed a doctoral dissertation based on Venus radar data collected at Goldstone in 
June 1963. After returning to JPL, Muhleman took a teaching position in the Cornell 
Astronomy Department in 1965. Shapiro had a Ph.D. in physics from Harvard and had 
worked on the detection of objects with radar in a clutter environment and on ballistic 
missile defense systems, before joining the team conducting radar experiments on Venus 
as the "guru" who calculated the ephemerides for Lincoln Laboratory planetary radar 
research. 54 



51. Spencer Jones, The Solar Parallax and the Mass of the Moon from Observations of Eros at the 
Opposition of 1931," Memoirs of the Royal Astronomical Society 66 (1938-1941): 11-66; Rabe, "Derivation of 
Fundamental Astronomical Constants from the Observations of Eros during 1926-1945," The Astronomical Journal 
55 (1950): 112-126; Fricke, "Inaugural Address Delivered at the lAU-Symposium No. 21," in Kovalevsky, 
pp. 12-13. 

52. Fricke, "Inaugural Address," p. 13; James B. McGuire, Eugene R. Spangler, and Lem Wong, The 
Size of the Solar System," Scientific American vol. 204, no. 4 (1961): 64-72. The value given in the article is 
92,925,100 8,500 miles, which I have converted into kilometers for consistency. 

53. Rechtin, p. 368; Muhleman, D. Holdridge, and N. Block, "Determination of the Astronomical Unit 
from Velocity, Range and Integrated Velocity Data, and the Venus-Earth Ephemeris," in Victor, Stevens, and 
Golomb, pp. 83-92. Kovalevsky, p. 1, provides a list of their names. 

54. Muhleman 8 April 1993; Muhleman 19 May 1994; Shapiro 30 September 1993; Evans 9 September 
1993. 



48 TO SEE THE UNSEEN 



The IAU symposium took place at the Paris Observatory between 27 and 31 May 
1963. By then, Lincoln Laboratory and JPL had refined the accuracy of their calculations 
even further, to 400 and 250 kilometers respectively. In his inaugural address, Walter 
Fricke lauded the accuracy and general agreement of the radar measurements. As far as 
Fricke and other symposium participants were concerned, the real debate was between 
the radar and dynamic methods. Spencer Jones' trigonometric method contained too 
many inherent sources of systematic error. In an attempt to reconcile the dynamic and 
radar methods, Brian G. Marsden, an astronomer at the Yale University Observatory, con- 
cluded in favor of the radar measurements. Rabe defended his method in person, argu- 
ing that the radar observations were inconsistent with the observed orbit of Eros and with 
gravitational theory. 55 

Muhleman and Shapiro supported the radar method and explained the basis on 
which JPL and Lincoln Laboratory had obtained their results. Additional support for the 
radar method came from Britain. D. H. Sadler, Superintendent of H. M. Nautical Almanac 
Office at the Royal Greenwich Observatory, read a paper on the results of the Jodrell Bank 
1962 Venus experiment. 

Lest it appear that there was unanimous approval of the radar method, COSPAR 
raised the question of the discrepancy between the radar observations of 1958 and 1959 
and those of 1961. Both Muhleman and Shapiro insisted that a discussion of the 1958 
data, which they both labelled "manifestly wrong," would be too difficult and serve no pur- 
pose. They explained that the 1958 technology was highly inadequate and stressed the 
harmonious agreement among the 1961 measurements. 56 

The participants unanimously adopted Resolution Six, which recommended that the 
astronomical constants be studied by both existing and new methods, so that the results 
might be compared. The IAU Executive Committee then translated Resolution Six into 
Resolution Four, which recommended that a working group study the system of astro- 
nomical constants, including the astronomical unit expressed in meters. Next, the IAU 
Executive Committee named the Working Group on astronomical constants: Dirk 
Brouwer, Jean Kovalevsky (Bureau of Longitudes, Paris), Walter Fricke (chairman), 
Aleksandr A. Mikhailov (director of the Pulkovo Observatory, Soviet Union) , and George 
A. Wilkins (Royal Observatory of Greenwich; Secretary). The Working Group sent a cir- 
cular letter and copies of the Paris resolutions to all persons, some 80 in number, who 
were thought to be likely to be able to help the Group or who might be affected by the 
introduction of new constants. The Working Group met in January 1964, at the Royal 
Greenwich Observatory, Herstmonceux Castle, and drew up a list of constants, including 
the astronomical unit, for consideration by the IAU general assembly, which met in 
Hamburg later that year. 57 

The Working Group met again during the Hamburg meeting on 27 August. 
Muhleman and Pettengill, who read Shapiro's paper in his place, reviewed the latest radar 
determinations of the astronomical unit by JPL and Lincoln Laboratory from new obser- 
vations made in 1964. Pettengill reported that preliminary analysis of the new data con- 
firmed a value of 149,598,000 kilometers, while Muhleman disclosed the JPL value of 



55. Kovalevsky, p. 3; Fricke, "Inaugural Address," pp. 12-13; Fricke, "Arguments in Favor of the Revision 
of the Conventional System of Astronomical Constants," in Pecker, p. 606; Marsden, "An Attempt to Reconcile 
the Dynamical and Radar Determinations of the Astronomical Unit," in Kovalevsky, pp. 225-236; Rabe, "On the 
compatibility of the Recent Solar Parallax Results from Radar Echoes of Venus with the Motion of Eros," in 
Kovalevsky, pp. 219-223. 

56. Shapiro, "Radar Determination of the Astronomical Unit," in Kovalevsky, pp. 177-215, and 
Muhleman, "Relationship between the System of Astronomical Constants and the Radar Determinations of the 
Astronomical Unit," in ibid., pp. 153-175; Kovalevsky, pp. 298 and 311. 

57. Kovalevsky, pp. 314 and 323; "Joint Discussion on the Report of the Working Group on the IAU 
System of Astronomical Constants," in Pecker, p. 600. 



FICKLE VENUS 49 



149,598,500 kilometers. The error of measurement reported by both laboratories, 100 
kilometers, was the smallest yet. 58 

Walter Fricke, chair of the Working Group, had misgivings about the radar method: 
"One could argue that the radar results are still too fresh to deserve full confidence. My 
personal distrust of them in so far as it originates in their newness has a counterpart in my 
distrust of the dynamical [Rabe] result obtained from the discussion of the observations 
of Eros." 59 

Without any discussion of the dynamic method, however, the Working Group rec- 
ommended adoption of a value expressed in meters and based on radar observations. The 
IAU general assembly then adopted the recommended value, 149,600 X 10 6 meters 
(149,600,000 kilometers). 60 It was now a matter of incorporating the new value into the 
various national almanacs and ephemerides. 

The Rotation of Venus 

The establishment of a highly accurate value for the astronomical unit and its adop- 
tion by the IAU was but one way that planetary radar demonstrated its value as a problem- 
solving scientific activity. The distance from Earth to Venus as measured by JPL radar also 
proved essential in keeping the 1962 Mariner 2 Venus probe on target. Early in its flight, 
Mariner 2 went off course. The Pioneer and Echo antennas sent midcourse commands, 
and a 34-minute maneuver put Mariner 2 on course. Had Rabe's value for the astronom- 
ical unit been used in place of the radar value, Mariner 2 would have passed Venus with- 
out acquiring any useful data. 61 

Valuable insight into the rotation of Venus further demonstrated the problem-solv- 
ing scientific merit of planetary radar. Optical and spectrographic methods failed to 
reveal the planet's period or direction of rotation, because Venus' thick, opaque cloud 
layer hid all evidence of its motion. Astronomers could only infer and imagine. Radar 
waves, on the other hand, were quite capable of penetrating the Venusian atmosphere; yet 
determining the planet's rotation by radar was still not easy. The key was methodical and 
meticulous attention to the shape of the echo spectra. Although JPL, Lincoln Laboratory, 
Jodrell Bank, and the Soviet Yevpatoriya facility calculated rotational rates for Venus, only 
JPL and Lincoln Laboratory found its "locked" orbit and retrograde motion. 62 

Evans and Taylor at Jodrell Bank published the first estimate of the planet's rota- 
tional period, about 20 days, using their erroneous 1959 data. In 1964, John Thomson 
reckoned a slow rotational rate, "probably" somewhere between 225 days and a similar ret- 
rograde period. After seeming to be on the brink of discovery, Thomson pulled back, con- 
cluding, "Future observations of the change of spectral width with time should enable the 
rotation rate and rotation axis to be determined." "Retrograde rotation," he held, was 
"physically unlikely." 63 



58. "Joint Discussion," pp. 591, 599 and 602-603; Shapiro, "Radar Determinations," in Pecker, 
pp. 615-623. 

59. "Joint Discussion," p. 606. 

60. Ibid., p. 606; "Report to the Executive Committee of the Working Group on the System of 
Astronomical Constants," in Pecker, p. 594. 

61. Renzetti 17 April 1992; Renzetti, A History, pp. 20 and 31; Renzetti, Tracking and Data Acquisition 
Support for the Mariner Venus 1962 Mission, Technical Memorandum 33-212 (Pasadena: JPL, 1 July 1965), pp. 9, 
17 and 75-76. 

62. RCA did not hesitate a guess on the rotation rate or direction. Maron, Luchak, and Blitzstein, pp. 
1419-1421. 

63. Evans and Taylor, p. 1359; Ponsonby, Thomson, and Imrie, "Radar Observations of Venus and a 
Determination of the Astronomical Unit," Monthly Notices of the Royal Astronomical Society 128 (1964): 14-16. 



50 TO SEE THE UNSEEN 



As close as Jodrell Bank came to discovering Venus' retrograde motion, the Soviets 
were that far away. Looking at frequency shifts in their 1961 data, Kotelnikov's group per- 
sistently estimated the planet's rotational period as 11 days, if not 9 or 10 days. They 
entirely missed the planet's retrograde motion. The Soviet error arose from their finding 
that the spectrum had a wide base, at least 400 hertz wide, indicating rapid motion. All 
British and United States workers agreed that the spectrum was far narrower. Lincoln 
Laboratory, for example, found a narrow spectrum of only 0.6 hertz. After their 1962 
radar study of Venus, Kotelnikov and his colleagues re-evaluated their data and conclud- 
ed a retrograde rotational period of 200 to 300 days. 64 

By then, though, JPL and Lincoln Laboratory already had discovered Venus' retro- 
grade motion. Finding it was not easy. Along the way, both laboratories concluded that the 
Venusian day was as long as its year, about 225 days. Venus was "locked" in its orbit, turn- 
ing one face always toward the Earth at the moment of inferior conjunction. However, 
these initial reports failed to note the planet's retrograde motion. 65 

The investigators who found it did not follow the same path of discovery. Just as the 
availability of technology had made planetary radar astronomy possible, the limits of that 
technology shaped the paths of discovery. JPL harvested the benefits of a powerful, low- 
noise continuous-wave radar in their 1962 and 1964 Venus experiment, while Lincoln 
Laboratory reaped the rewards of their computer and signal processing skills. 

The Goldstone radar permitted Roland L. Carpenter to find the retrograde motion 
of Venus in a rather novel fashion. Carpenter actually had a BA in psychology from 
California State University at Los Angeles, but he had been interested in astronomy since 
childhood, and he had worked at Griffith Observatory as a guide. Finding very little work 
available in psychology, Carpenter found a job at Collins Radio as an electrician thanks to 
his friend, astronomer George Abell (known for Abell's clusters of galaxies), who had a 
summer job there. Carpenter gradually worked his way up to electronics engineer, simply 
through his work experience at Collins Radio. Then, when JPL began hiring people with 
experience in radio communications for the Deep Space Network, Carpenter jumped at 
the opportunity. Carpenter worked with Dewey Muhleman in Walt Victor's group and 
took advantage of JPL's employee benefits program by pursuing an advanced degree in 
astronomy at UCLA, while working full-time at JPL. His doctoral dissertation, 'The Study 
of Venus by CW Radar," written under Lawrence Aller and completed in 1966, used data 
from the 1964 JPL Venus radar experiment. 66 By then, however, Carpenter already had 
published his discovery of the retrograde rotation of Venus. 67 



64. Kuznetsov and Lishin, pp. 199-201; Kotelnikov, "Radar Contact with Venus, "Journal of the British 
Institution of Radio Engineers 22 (1961): 295; Kotelnikov et al, "Results of Radar Contact," p. 1732; Kotelnikov, 
Dubrovin, M. D. Kislik, Korenberg, Minashin, Morozov, Nikitskiy, Petrov, Rzhiga, and Shakhovskoy, "Radar 
Observations of the Planet Venus," Soviet Physics Doklady 7 (1963): 728-731; Kotelnikov, Dubrovin, V. A. 
Dubinskii, Kislik, Kusnetsov, Lishin, Morozov, Petrov, Rzhiga, G. A. Sytsko, and Shakhovskoy, "Radar 
Observations of Venus in the Soviet Union in 1962," Soviet Physics Doklady 8 (1964): 644; Smith, p. 15. Rzhiga, 
"Radar Observations of Venus in the Soviet Union in 1962," in M. Florkin and A. Dollfus, eds. Life Sciences and 
Space Research II (New York: Interscience Publishers, 1964), pp. 178-189, states 300 days but still misses the ret- 
rograde motion. 

65. Pettengill et al, "A Radar Investigation of Venus," pp. 189-190; Pettengill, "Radar Measurement of 
Venus," in Priester, pp. 880-883. The range given was between 115 and 500 days, that is, 225 (+275, -110) days. 
The first JPL external announcement of that finding was made in a paper read by Solomon Golomb and 
Leonard R. Mailing at a convention on radio techniques and space research held at Oxford in July 1961. Mailing 
and Golomb, pp. 297-303. The paper was not published until October 1961 and was preceded in print by the 
internal report, Victor and Stevens, "Summary and Conclusions," pp. 94-95. See also Victor and Stevens, 
"Exploration of Venus by Radar," pp. 46-47; Muhleman, "Early Results of the 1961 JPL Venus Radar 
Experiment," The Astronomical Journal 66 (1961): 292; Victor and Stevens, "The 1961 JPL Venus Radar 
Experiment," p. 94. 

66. Carpenter, telephone conversation, 14 September 1993. 

67. Carpenter, "An Analysis of the Narrow-Band Spectra of Venus," in JPL Research Summary No. 36-14 for 
the Period February 1, 1962 to April 1, 1962 (Pasadena: JPL, 1 May 1962), pp. 56-59. 



FICKLE VENUS 



51 



His first announcement of the planet's retrograde motion appeared in a JPL inter- 
nal report dated 1 May 1962 and was based on the 1961 Venus experiment. Carpenter sug- 
gested a retrograde rotational period of about 150 days, but backed off from insisting on 
his discovery. "Unfortunately," Carpenter concluded, "a definitive answer cannot be given 
for the rotation period of Venus based on the present data." 

Carpenter hesitated until he had the results of the Goldstone 1962 Venus experi- 
ment. Between 1 October and 17 December 1962, when Venus was closest to Earth, 
Goldstone made nearly daily radar observations of the planet with a 13-kilowatt continu- 
ous-wave transmitter operating at 2388 MHz (12.6 cm). Equipped with a maser and a para- 
metric amplifier, the system's total noise temperature was only 40 K, better than the 64 K 
achieved in 1961. 68 

The Goldstone radar was sufficiently powerful and sensitive that a large feature on 
the planet's surface showed up as an irregularity or "detail" on the power spectrum. The 
surface feature scattered back to the radar antenna more energy than the surrounding 
area. Normally, most spectral irregularities resulted from random fluctuations produced 
by noise. The power and sensitivity of the Goldstone radar made all the difference. 

"On close examination," Carpenter wrote, "one irregularity was found to persist from 
day to day and to change its position slowly.. ..The relative permanence of the detail strong- 
ly suggests that it was caused by an actual physiographic feature on the surface of Venus 
and that its motion was the result of the planet's rotation. The true nature of the feature 
can only be guessed at; however, it is not unreasonable to assume that it is a particularly 
rough region of rather large extent." 













j 


C "" 














1 2 


V ' 1WO 






2 


V '- 






i 


2 


1 n;0(U 














___../ 


-Taj 






/ 


I IVtVU 














'RtOUtNC 


T, en 





FigureS 

Lower portion of the. spectra obtained by Roland Carpenter 
during the week prior to the 1 962 conjunction of Venus. 
Note the persistent detail on the left side of each spectrum. 
Carpenter followed that detail to determine the retrograde 
motion of Venus. (Courtesy of Jet Propulsion Laboratory.) 



68. Carpenter, telephone conversation, 14 September 1993; Goldstein and Carpenter, "Rotation of 
Venus: Period Estimated from Radar Measurements," Science 139 (1963): 910; Carpenter, "Study of Venus by CW 
Radar," The Astronomical Journal 69 (1964): 2. Details of the 1962 JPL Venus radar experiment are given in 
Goldstein, Stevens, and Victor, eds., Radar Exploration of Venus: Goldstone Observatory Report for October-December 
1962, Technical Report 32-396 (Pasadena: JPL, 1 March 1965). 



52 TO SEE THE UNSEEN 



Carpenter then followed the movement of this "detail" in order to deduce the plan- 
et's rotational period. He calculated that Venus had either a forward period of about 1200 
days or a retrograde period of 230 days from one conjunction to the other. Next, he mea- 
sured the bandwidth of the lower portion of the spectra; their widths were incompatible 
with a 1200-day forward rotation. The base bandwidth measurements, however, did 
"strongly suggest that the sidereal rotation period of Venus is not synchronous, but rather 
250 40 days retrograde." 69 

Millstone lacked the power and sensitivity of Goldstone. The discovery of Venus' 
retrograde motion at Lincoln Laboratory by William B. Smith relied instead on his 
computer and signal analyzing skills. Although Smith preceded Carpenter in announcing 
the retrograde motion of Venus in a publication, he did not achieve recognition as its 
discoverer. 

Smith looked at the spectral bandwidths of radar returns on 11 separate days 
between 2 April and 8 June 1961. Like Carpenter, he failed to verify a synchronous rota- 
tion; however, Smith came to realize that the way the signal bandwidth changed over time 
could be explained only by retrograde motion. He wrote up his findings and submitted 
them to his supervisor, Paul Green, for approval. Smith wanted to feature the planet's ret- 
rograde motion in his paper, but Green remembered an earlier episode, when "we had 
been badly burned." That was the embarrassment of 1958. 

Green hesitated. Uranus was the only planet then known to have a retrograde peri- 
od, "but that one is way the hell out, and who would have thought that the next planet to 
the Earth would have had that kind of anomalous behavior?" Green admitted, "I guess I 
was working more on psychological factors than on anything else. So I had Bill tone it 
down." The published article's abstract read: 'The (relatively weak) result implies a very 
slow or possibly retrograde rotation of the planet." The article itself contained no state- 
ment of the planet's retrograde motion. 70 

The watered down version made all the difference. Carpenter published his explicit 
and unequivocal results jointly with fellow JPL radar astronomer Dick Goldstein in the 
8 March 1963 issue of Science, while the February 1963 issue of The Astronomical Journal 
carried Smith's suggestive abstract. 71 

Green regretted his decision. "Bill Smith is the man who discovered that Venus has 
retrograde spin, and he should go down in the history books. Due to me he didn't, 
because his paper didn't feature it the way it should have. If I hadn't sat on it, it would 
have featured it, but as it came out, it didn't. The people that look at the fine print real- 
ize that he had that message, that that was what his data showed, but it didn't make the 
big splash and give him the career achievement that he deserved." 72 Fellow Lincoln 
Laboratory radar astronomer Irwin Shapiro concurred: "I felt he [Smith] got a raw deal, 
because he made a major discovery for which he never got credit." 73 

The detection of Venus, the measurement of the size of the astronomical unit, and 
the determination of the rotational period and direction of Venus formed the foundation 
on which planetary radar astronomy was laid. Planetary radar advanced by solving prob- 
lems left unresolved or at best unsatisfactorily resolved by optical methods. Deliberately or 
not, the problems solved supported the NASA mission to explore the solar system. Driving 
the new scientific activity was the availability of a new generation of radars built for mili- 
tary defense (at Lincoln Laboratory) and for space exploration (at JPL). The limits of that 
technology shaped the paths of discovery. 



69. Carpenter, "Study of Venus by CW Radar," pp. 4-6; Carpenter, telephone conversation, 14 
September 1993. 

70. Green 20 September 1993; Smith 29 September 1993; Smith, pp. 15-21. 

71. Goldstein and Carpenter, pp. 910-911; Smith, pp. 15-21. Internal evidence indicates that Science 
received the paper on 15 January 1963. 

72. Green 20 September 1993. 

73. Shapiro 30 September 1993. 



FICKLE VENUS 53 



Without technology and without funding, planetary radar astronomy was impossible. 
The emergence of planetary radar coincided with the creation of a national, civilian space 
agency, NASA, a national, civilian agency to fund scientific research, the National Science 
Foundation (NSF) , and a national, military space research agency, ARPA. It also paralleled 
the rise of American radio astronomy and the age of the Big Dish. Standing at the inter- 
section of civilian and military research into space, the ionosphere, the Moon, and the 
Sun, planetary radar offered much to potential patrons. It was a wonderful and unique 
time to organize a new scientific activity. 



Chapter Three 

Sturm und Drang 



The period between 1958 and 1964 saw the explosive growth of planetary radar 
astronomy in terms of the number of active facilities and investigators. Investigators in 
three countries (the United States, Britain, and the Soviet Union) attempted to detect 
Venus in 1961, and three facilities in the United States alone (Lincoln Laboratory, JPL, 
and RCA) succeeded. During the 1962 conjunction, the Jicamarca Radar Observatory, a 
National Bureau of Standards ionospheric facility in Peru, made radar observations of 
Venus at 50 MHz (6 meters) . At the same time, the Lincoln Laboratory solar radar facili- 
ty at El Campo, Texas, completed in the summer of 1960, observed Venus at 38 MHz (8 
meters). 1 Thus, by 1964, five American facilities had performed radar experiments on 
Venus. 

The creation of radar astronomy courses, a textbook, and a conference dedicated 
solely to radar astronomy also signalled the emergence of a new and rapidly growing 
scientific field. As it had in carrying out planetary radar experiments, Lincoln Laboratory 
took the lead in shaping the new field. In addition to organizing radar astronomy cours- 
es and a textbook, Lincoln Laboratory sponsored the first, and only, radar astronomy 
conference and undertook, in association with the Cambridge astronomical community, 
a campaign to design and build a new radar research instrument. 

MIT routinely offered summer courses and asked Lincoln Laboratory to propose 
some. As John Evans explained, "Radar astronomy was in vogue, we were just entering the 
Space Age, and Sputnik had been launched." So Lincoln Laboratory agreed to run a sum- 
mer school in radar astronomy beginning in August 1960. In all, about twenty people gave 
lectures. Evans talked about lunar radar astronomy. Jack Harrington, head of the Radio 
Physics Division of Lincoln Laboratory and in charge of the summer course, promised lec- 
turers that the talks would be organized into a book. As it turned out, Evans recalled, "the 
lecture notes weren't that good. We were all asked to rewrite them." 2 

In August 1961, Harrington and Evans ran the radar astronomy summer course 
again. The topics and lecturers were somewhat different; the course of 15 lectures lasted 
only one week. Among the lecturers were Paul Green, Bob Kingston (who had designed 
the maser for the 1958 Venus experiment), Gordon Pettengill, Bob Price, Herb Weiss 
(who had built Millstone), and Victor Pineo (formerly of the National Bureau of 
Standards) . Von Eshleman (Stanford) , a guest lecturer, discussed solar radar experiments. 
The week ended with a two-hour tour of the Millstone Hill Radar Observatory led by 
Pettengill, Pineo, and Evans "to observe firsthand a modern space radar facility and to wit- 
ness a representative experiment in radar astronomy." 3 



1. W. K. Klemperer, G. R. Ochs, and Kenneth L. Bowles, "Radar Echoes from Venus at 50 Me/sec," The 
Astronomical Journal 69 (1964): 22-28; Overhage to Lt. Gen. James Ferguson, 28 March 1963, MITA; Jesse C. 
James, Richard P. Ingalls, and Louis P. Rainville, "Radar Echoes from Venus at 38 Me/sec," The Astronomical 
Journal 72 (1967): 1047-1050. 

2. Evans 9 September 1993. MITA does not have a copy of the 1960 summer course lecture notes. 

3. Brochure, MIT, Radar Astronomy: Summer Session 1961 August 14-18 (Cambridge: MIT, 1961), LLLA; 
MIT, Radar Astronomy: Summer Session MIT, August 14-18, 1961, Lectures 1-15, 3 vols. (Cambridge: MIT, 1961), 
MITA. 

55 



56 TO SEE THE UNSEEN 



The radar astronomy summer course was not given again, "largely because the peo- 
ple concerned have been occupied with other commitments," Evans later wrote. 4 Price 
and Green were no longer involved in radar astronomy, and Pettengill had left Lincoln 
Laboratory. Harrington himself became Director of the MIT Center for Space Research, 
which he founded with funding from NASA in 1963. 

At the end of the 1961 summer course, the lecture notes were assembled into a three- 
volume tome. Yet, as Evans explained, "We didn't have a good set of course notes that 
would constitute a book." 5 Paul Green became irritated with the lack of progress on the 
project, announced that he would no longer contribute any material to the book, and 
nominated Evans to take over the project from Harrington. Evans found himself in an 
awkward situation; Harrington was his boss. Fortunately, Wilbur B. Davenport, Jr., one of 
the Assistant Directors of Lincoln Laboratory, had an interest in radar astronomy and 
pressured Harrington to get the book done quickly. 

Evans recalled: "So my arm got twisted very hard by Davenport. I really didn't want 
to do it. I was quite busy, and I didn't want to take over Jack's project, so I resisted. I even- 
tually capitulated after enough pressure on the condition that a) I had somebody to help 
me, and b) I had a secretary assigned to do typing and nothing else, because part of the 
problem was just getting material out of rough draft form and into typed form. They 
agreed to both of those conditions." Tor Hagfors, a graduate of Scandinavian technical 
schools and the Stanford University electrical engineering program, edited the book with 
Evans. 

Next, the project met difficulty at the publisher. The McGraw-Hill editor who had 
been handling the project left, but no one at Lincoln Laboratory knew. 'The manuscript 
sat in his drawer for almost two years," Evans related. "Meanwhile, we were thinking that 
the manuscript was going through proofing and so on. Finally, we got a letter from some 
guy who had inherited this desk and found this manuscript. He got it printed fairly quick- 
ly, but in sort of photo-offset form rather than nice copy. At least it came out, belatedly." 

Once McGraw-Hill published Radar Astronomy in 1968, radar astronomy had a text- 
book, parts of which are still used to teach radar astronomy. Nonetheless, neither MIT nor 
Lincoln Laboratory (which is not a teaching institution) offered a course in radar astron- 
omy until 1970. 6 Although the Evans-Hagfors textbook and the MIT summer course might 
have served to train a generation of radar astronomers, they did not. Planetary radar 
astronomy was the child of a research center (Lincoln Laboratory) , not an educational 
institution (MIT) . As a result, Lincoln Laboratory radar astronomers did not reproduce 
themselves in a traditional academic fashion through graduate education, but through 
employment. 

Three radar astronomers came to Lincoln Laboratory during the 1960s through 
employment: Stanley H. Zisk, Richard P. Ingalls, and Alan E. E. Rogers. Zisk, who created 
lunar radar images for NASA in support of the Apollo program, and Haystack Associate 
Director Dick Ingalls, who had been a Lincoln Laboratory employee since 1953, both had 
degrees in electrical engineering. Alan Rogers, born in Salisbury, Rhodesia (now 
Zimbabwe), earned a Ph.D. in electrical engineering from MIT in 1967, and was trained 
in radio astronomy, before carrying out radar astronomy experiments. 7 

As far as defining the field of radar astronomy, and particularly in terms of defining 
actual and potential patrons, the most important step taken by Lincoln Laboratory was 



4. Evans and Tor Hagfors, eds., Radar Astronomy (New York: McGraw-Hill Book Company, 1968) , p. viii. 

5. Evans 9 September 1993. 

6. Campbell 9 December 1993; E-mail, Pettengill to author, 29 September 1994; Rogers 5 May 1994. 

7. Pettengill 28 September 1993; Rogers 5 May 1994; NEROC, "Technical Proposal: Radar Studies of 
the Moon (Topography)," 12 November 1971, SEBRING. 



STURM UND DRANG 57 



the organization of a conference on radar astronomy. Never again did another such con- 
ference take place, mainly because radar astronomers located themselves within existing 
professional organizations. Moreover, the small number of radar astronomers never justi- 
fied the creation of a separate society or journal. 

The conference underscored the Big Science environment in which radar astrono- 
my was evolving. Only a few attempts at Venus had been made by Lincoln Laboratory and 
Jodrell Bank when the conference convened; lunar, meteor, and ionospheric radar stud- 
ies were well established. Those radar studies were part of growing civilian and military 
programs in ionospheric and communication research. More importantly for planetary 
radar, a new civilian space agency, NASA, had been created only the year before. Its cre- 
ation, and the prospect of participating in space research, eventually shaped the new field 
of planetary radar astronomy more than any other Big Science patron. 

The Conference on Radar Astronomy 

The National Academy of Sciences, through its Space Science Board, underwrote 
the radar astronomy conference. Established in 1958, the Space Science Board main- 
tained liaisons with the National Science Foundation, NASA, ARPA, the Office of the 
Science Advisor to the President, and other federal agencies participating in the country's 
space program. The Space Science Board solicited the opinions of scientists through dis- 
cussions and summer studies and recommended space programs to federal agencies. 8 

Bruno B. Rossi, a member of the Space Science Board and a leading MIT physics 
professor, organized the radar astronomy conference. Rossi had undertaken experimen- 
tal research on cosmic rays in the 1930s, before working at Los Alamos Laboratory during 
World War II. He joined MIT in 1946. In 1958, coincidentally with the creation of NASA, 
Rossi began to consider the potential value of direct measurement of the ionized inter- 
planetary gas by space probes. 9 

Thomas Gold, recently hired to head Cornell's Center for Radiophysics and Space 
Research, the parent organization for its radio and radar telescope, and MIT's Philip 
Morrison, both members of the Space Science Board, assisted Rossi in organizing the con- 
ference; however, the brunt of the actual work fell on Rossi's shoulders. He reserved MIT's 
Endicott House in Dedham, Massachusetts, for 15 and 16 October 1959. Endicott House 
had a dining area, meeting rooms, large gardens, and accommodations for 8 people; the 
remainder were lodged at a nearby hotel. 

Rossi saw the conference as a small group meeting to develop concrete recommen- 
dations for consideration by the Space Science Board at its October meeting. The origi- 
nal conference title, "Reflections and Scattering of Radar Signals Beyond Several Earth 
Radii," by definition excluded ionospheric radar. However, the revised name, 
"Conference on Radar Astronomy," was less unwieldy and did not appear to exclude those 
interested in ionospheric research. 10 

Holding a different vision of the conference was Stanford professor of electrical engi- 
neering Von R. Eshleman. Seeking to exploit the creation of NASA, Eshleman proposed 
radar studies of planetary ionospheres and atmospheres from spacecraft. Such studies 
were a logical extension of Stanford's ionospheric radio and radar work of the 1950s, 
which included a pioneering solar radar experiment. 



8. Space Science Board, Proposal for Continuation of Contract NSR 09012-903, 28 October 1965, 
"NAS-SSB, 1965," NHO; Joseph N. Tatarewicz, Space, Technology, and Planetary Astronomy (Bloomington: Indiana 
University Press, 1990) , p. 38. 

9. Rossi biographical information, MITA; "President's Report Issue," MIT Bulletin vol. 82, no. 1 (1946): 
137-138. 

10. "Conference on Radar Astronomy Program," n.d., and George A. Derbyshire, Memorandum for the 
Record, 29 May 1959, "ORG, NAS, 1959 October Space Science Bd., Conferences Radar Astronomy, Dedham," 
NAS. Hereafter, Conference Program and Derbyshire Memorandum, 29 May 1959, respectively. 



58 TO SEE THE UNSEEN 



In 1959, contemporary with the first radar attempts at Venus, Eshleman and Philip 
B. Gallagher of Stanford, with Lt. Col. Robert C. Barthle of the U.S. Army Signal Corps, a 
Stanford graduate student, attempted to bounce radar waves off the solar corona. The Air 
Force Cambridge Research Center (AFCRC) underwrote the Stanford experiment, and 
the Office of Naval Research funded the 46-meter (150-ft) dish antenna constructed for 
ionospheric research under the direction of Oswald Villard. Although Eshleman claimed 
success, a comparison of his results with those obtained shortly afterward by the El Campo 
solar radar cast serious doubt about their validity, which some radar astronomers contin- 
ue to express. 11 

As planning for the radar conference was underway, Eshleman was preparing the 
solar radar experiment and was on the point of campaigning NASA to underwrite studies 
of planetary ionospheres from spacecraft. It was a pivotal moment for calling attention to 
the Stanford radar work. Eshleman saw the conference as a Stanford opportunity. In a let- 
ter to Rossi, he claimed that Stanford already "had begun to plan some kind of a meeting 
to bring together all who are active in this field. However these plans had [sic] not pro- 
gressed very far." He proposed a larger conference with Stanford and the Stanford 
Research Institute (SRI) "as co-hosts." If the AFCRC were invited to co-sponsor the con- 
ference, Eshleman suggested, part of the travel expenses for foreign visitors might be cov- 
ered. Conference papers could be published as a group in the Proceedings of the Institute 
of Radio Engineers. 12 

The conference, however, was solely an MIT affair sponsored only by the National 
Academy of Sciences. The spectrum of United States civilian and military scientific radar 
research facilities was represented: MIT and Lincoln Laboratory, Stanford and SRI, 
Cornell University, the NRL, and the National Bureau of Standards CRPL. In addition, 
radio astronomers were invited from Harvard University, Yale University, the University of 
Michigan, and the National Radio Astronomy Observatory (NRAO), Green Bank, West 
Virginia, the country's major radio astronomy center. ARPA and the AFCRC represented 
the military. 

In addition to representatives of the Space Science Board, Rossi invited the National 
Science Foundation program director for astronomy and NASA Space Science chief 
Homer E. Newell, Jr. Unable to attend, Newell recommended Nancy G. Roman in his 
place: "Although we have no program which directly involves radar astronomy, Dr. Roman 
will be happy to discuss those aspects of our Astronomy and Astrophysics Programs which 
are related to this field. I am sure that the results of the discussion will be valuable in our 
program planning." 13 Roman was a felicitous choice; she had carried out lunar radar stud- 
ies at the NRL. 14 



11. Eshleman, telephone conversation, 26 January 1993; Eshleman 9 May 1994; Eshleman, Barthle, and 
Gallagher, "Radar Echoes from the Sun," Science 134 (1960): 329-332; Eshleman and Allen M. Peterson, "Radar 
Astronomy," Snentifec American 203 (August, 1960): 50-51; Barthle, The Detection of Radar Echoes from the Sun, 
Scientific Report 9 (Stanford: RLSEL, 24 August 1960); Pettengill 28 September 1993. 

The possibility of obtaining radar echoes from the solar corona had been suggested earlier by the 
Australian ionosphericist Frank Kerr in 1952 and by the Ukrainians F. G. Bass and S. I. Braude in 1957. Kerr, 
"On the Possibility of Obtaining Radar Echoes from the Sun and Planets," pp. 660-666; Bass and Braude, "[On 
the Question of Reflecting Radar Signals from the Sun] ," Ukrains "ky Fizychny Zhurnal [Ukrainian Journal of Physics] 
2 (1957): 149-164. 

12. Eshleman to Rossi, 13 May 1959, "ORG, NAS, 1959 October Space Science Bd., Conferences Radar 
Astronomy, Dedham," NAS. 

13. "Preliminary List of Invitees;" "Draft Recommendations of the Conference on Radar Astronomy," 
Appendix A, "List of Participants;" Newell to Rossi, 18 June 1959; Derbyshire Memorandum, 29 May 1959; and 
Derbyshire, Memorandum for the Record, 2 June 1959, "ORG, NAS, 1959 October Space Science Bd., 
Conferences Radar Astronomy, Dedham," NAS. 

14. For Roman's lunar radar work at the NRL, see, for example, Yaplee, Roman, Craig, and T. F. 
Scanlan, "A Lunar Radar Study at 10-cm Wavelength," in Bracewell, ed., Paris Symposium on Radio Astronomy 
(Stanford: Stanford University Press, 1959), pp. 19-28, and Ch. 1, note 69. 



STURM UNO DRANG 59 



Invitations to foreign radio and radar investigators went to Jodrell Bank, the Royal 
Radar Establishment (Malvern, England), the Division of Radiophysics of the Australian 
Commonwealth Scientific and Industrial Research Organization (CSIRO), the Chalmers 
University of Technology Research Laboratory of Electronics (Gothenburg, Sweden), and 
the Canadian Defense Research Board Telecommunications Establishment. No Soviet sci- 
entists were invited. 

The conference program highlighted the work of Lincoln Laboratory. After a talk by 
Thomas Gold (Cornell) on the scientific goals of radar astronomy, Jack Harrington 
(Lincoln Laboratory) explained certain experimental techniques and Herb Weiss 
(Lincoln Laboratory) spoke on transmitters, receivers, and antennas. Next Paul Green 
(Lincoln Laboratory) discussed signal detection and processing, and James Chisholm 
(Lincoln Laboratory) talked about electromagnetic propagation phenomena. In another 
session, organizations represented at the conference described their research programs. 
General discussion and the formulation of recommendations took up the second day. 15 

These recommendations defined radar astronomy as a field especially useful to 
NASA and the rapidly growing space effort. The arguments set forth appeared as attempts 
to garner the patronage of the new space agency. The first recommendation, for example, 
spoke directly to NASA and argued the value of radar astronomy for planetary explo- 
ration. Launching spacecraft required precise measurements of interplanetary distances 
and knowledge of planetary surface and atmospheric conditions, all of which radar 
astronomy was capable of providing. "The importance of radar astronomy to the efficient devel- 
opment of space science must not be underestimated, " the recommendation exhorted. 

Additional recommendations urged the construction of new radar astronomy facili- 
ties operating at a variety of frequencies, as well as the design and construction of large 
dish and array antennas, high-power high-frequency transmitters, and signal detection 
and recording techniques. The construction of radar telescopes, the conference recom- 
mendations argued, would be far less expensive than building and sending planetary 
probes. 

Conference recommendations also addressed the military and radio astronomy. 
Planetary radar astronomy at Lincoln Laboratory would not have existed without the con- 
struction of the Millstone Hill radar, which the military funded. However, planetary radar 
experiments officially did not exist; military research was the first priority. Radar astrono- 
my, the recommendations pleaded, needed facilities of its own, where it would receive top 
priority and be "viewed as pure science." 

Conference recommendations also targeted radio astronomers. "Where large radio tele- 
scopes are being planned or built, " one recommendation proposed, "serious consideration be 
given from the beginning to the incorporation of provisions for a high-powered transmitter, even if a 
transmitter were not actually installed." The recommendation further suggested specifi- 
cally that a radar transmitter be installed on the 10-GHz (3-cm) 43-meter (140-ft) NRAO 
antenna, thereby offering "an excellent opportunity for radar investigations at very high 
frequencies." While recognizing that the dissimilar needs of radar and radio astronomers 
often gave rise to conflict, one recommendation stated, compromise could resolve them. 16 
As we shall see later, however, those dissimilar needs were beyond compromise. 

Bruno Rossi submitted the conference draft recommendations to the Space Science 
Board at its October 1959 meeting. After some editing and checking that left the recom- 



15. Derbyshire Memorandum, 2 June 1959; Conference Program; Rossi to Derbyshire, 10 June 1959, 
"ORG, NAS, 1959 October Space Science Bd., Conferences Radar Astronomy, Dedham," NAS. 

16. "Draft Recommendations of the Conference on Radar Astronomy," pp. 58, "ORG, NAS, 1959 
October Space Science Bd., Conferences Radar Astronomy, Dedham," NAS. Emphasis in original text. 



60 TO SEE THE UNSEEN 



mendations unaltered, the Space Science Board endorsed them for distribution to fund- 
ing agencies and other interested groups. 17 Endicott House was the last conference dedi- 
cated solely to radar astronomy, though radar astronomers continued to meet under an 
existing organizational umbrella, one dedicated not to planetary science, since such spe- 
cialized organizations did not yet exist, but to radio astronomy and electrical engineering. 

L' Union Radioscientifique Internationale 

Although much of the earliest radar astronomy work grew out of an interest in ionos- 
pheric questions, ionosphericists and planetary radar astronomers soon went separate 
ways. Planetary radar astronomers grew closer to their colleagues in radio astronomy, with 
whom they shared techniques and technologies, such as antennas and low-noise receivers. 
The shift of planetary radar astronomy from the ionospheric to the radio astronomy com- 
munity was manifest within the Union Radioscientifique Internationale (URSI), which 
quickly became the premier forum for planetary radar astronomers. 18 

URSI was an international radio science organization founded in France in 1921 by 
Gustave Ferric and other French radio pioneers. 19 Its big tent sheltered a range of fields, 
including ionospheric and radio astronomy science, united by a common technical inter- 
est in what might be called radio science. Lacking telescopes committed entirely to their 
field, planetary radar astronomers worked side-by-side with radio astronomers at the same 
observatory. As radar astronomer Donald B. Campbell has observed, There is a tremen- 
dous amount of cross-fertilization between planetary radar and radio astronomers in 
terms of techniques and equipment." 20 These shared technical interests and instruments 
brought planetary radar and radio astronomers together at URSI meetings. 

Radio astronomers had had their own commission within URSI since shortly after 
World War II. In 1946, at its General Assembly meeting in Paris, URSI created a special 
subcommission on Radio Noise of Extra-Terrestrial Origin, which became Commission 5, 
Extra-Terrestrial Radio Noise, when URSI revised its commission structure at its 1948 
Stockholm meeting. On the proposal of the U.S. National Committee, Commission 5 
became the Commission on Radio Astronomy two years later at the General Assembly 
meeting in Zurich. Commission 5 concerned itself with radio astronomy, as well as obser- 
vations of meteors and the Moon "by radio techniques," meaning by radar. Thus, for 
example, at the Paris URSI symposium on radio astronomy held in July 1958, a number 
of papers featured the latest lunar radar work by U.S. and British investigators. 21 

The first URSI meeting at which planetary radar astronomers gave papers took 
place in San Diego, California, between 19 and 21 October 1959, immediately following 
the Endicott House Conference on Radar Astronomy. The meeting included a first-of-its- 
kind symposium on radar astronomy. However, presenting the panel discussion was not 
Commission 5, but URSI Commission 3, Ionospheric Radio. 



17. Memorandum, E. R. Dyer, Jr., to Participants, Space Science Board Conference on Radar 
Astronomy, 30 October 1959, and "Report and Recommendations of the Conference on Radar Astronomy," 
"ORG: NAS, 1959 October Space Science Bd.: Conferences Radar Astronomy: Dedham," NAS. 

18. Pettengill 29 September 1993. 

19. URSI actually dates back to 1913 and the creation of the French Commission Internationale de TSF 
Scientifique. TSF (Telegraphic Sans Fil) is French for wireless radio. Albert Levasseur, De la TSF a I'electronique: 
Histoire des techniques radioelectriques (Paris: ETSF, 1975), pp. 79 and 87. 

20. Campbell 9 December 1993. 

21. Edge and Mulkay, p. 44; Bracewell, Paris Symposium, passim. 



STURM UND DRANG 61 



The seven panel members, all of whom had participated in the Endicott House con- 
ference, were practicing radar astronomers at the NRL, Jodrell Bank, Stanford, Lincoln 
Laboratory, Cornell, and the National Bureau of Standards. Von Eshleman was the panel 
moderator. The speakers covered lunar, solar, meteor, auroral, and planetary radar, as well 
as radar studies of the exosphere and the interplanetary medium. The symposium was of 
some historical importance: Paul Green described planetary range-Doppler imaging, 
which later became a central planetary radar technique. 22 

By the URSI Tokyo meeting of September 1963, planetary radar astronomy had 
moved to the newly renamed Commission 5, Radio and Radar Astronomy. Twenty institu- 
tions reported on recent U.S. developments in the two fields. The meeting also brought 
together individuals from related areas, such as Commission 7, Radio Electronics, where 
investigators reported on parametric amplifiers, masers, and other microwave devices of 
interest to planetary radar astronomers. 23 

Although the electronic side of planetary radar astronomy drove it to attend URSI 
meetings and to publish in such journals as the Proceedings of the IRE, the astronomy side 
pulled it toward meetings of the International Astronomical Union (IAU) and the 
American Astronomical Society (AAS) and to publication in astronomy and general sci- 
ence journals, primarily The Astronomical Journal, Science, and Nature. These institutional 
and publication forums, though, did not meet the need for specialized discussion of plan- 
etary topics. 

Sporadic workshops provided only limited forums. For example, the 1962 inferior 
conjunction of Venus furnished the occasion for a symposium on radar and radio obser- 
vations of that planet. Although planetary radio astronomers delivered most of the sym- 
posium papers, radar astronomers Roland Carpenter, Dick Goldstein, and Dewey 
Muhleman described the latest radar research on Venus. 24 Aside from a preliminary 
report by National Bureau of Standards ionospheric researchers on their one-time-only 
radar attempt at Venus, the symposium was strictly a JPL affair. 

Starting in 1965, the need for a specialized forum for presenting and discussing 
radar research began to be met through a joint URSI-IAU Symposium on Planetary 
Atmospheres and Surfaces held at Dorado, Puerto Rico, 24-27 May 1965. The Organizing 
Committee included radar astronomers John Evans, Dewey Muhleman, and Gordon 
Pettengill, while Evans and Pettengill chaired sessions on lunar and planetary radar 
astronomy. The latter session brought together practitioners from Lincoln Laboratory, 
JPL, Cornell's nearby observatory at Arecibo, and the Soviet Union. 25 

A conference on lunar and planetary science held during the week of 13 September 
1965 and organized by Caltech and JPL also had its share of planetary radar papers. 
Researchers from JPL, Jodrell Bank, and Cornell's Arecibo Observatory spoke on Venus, 
while JPL and Arecibo representatives read papers on Mars. Noticeably absent, however, 
were researchers from Lincoln Laboratory, which was still a major planetary radar 
research center. 26 



22. Ray L. Leadabrand, "Radar Astronomy Symposium Report," Journal of Geophysical Research 65 (April 
1960) : 1 103-1 1 15; Green 20 September 1993. P. Green to author, 21 December 1994, states that Green described 
range-Doppler mapping in his earlier talk at the Endicott House conference, but the talk was not published. 

23. "URSI National Committee Report, XIV General Assembly, Tokyo, September, 1963: Commission 5. 
Radio and Radar Astronomy, "Journal of Research of the National Bureau of Standards, Section D: Radio Science 68D 
(May 1964): 631-653; "Commission 7. Radio Electronics," ibid., pp. 655-678. 

24. The symposium papers were published in The Astronomical Journal 69 (1964): 1-72. The Astronomical 
Journal is the publication of the American Astronomical Society. 

25. William E. Gordon, "Preface, "Journal of Research of the National Bureau of Standards, Section D: Radio 
Science 69D (July-December 1965): iii. This was a special issue containing the symposium papers. 

26. Harrison Brown, Gordon J. Stanley, Duane O. Muhleman, and Guido Munch, eds., Proceedings of the 
Caltech-JPL Lunar and Planetary Conference (Pasadena: Caltech and JPL, 15 June 1966). 



62 TO SEE THE UNSEEN 



Planetary radar astronomy is at the convergence of science and engineering. 
Attendance of radar astronomers at both IAU and URSI meetings during the 1960s 
reflected the dichotomous nature of radar astronomy, perched between radio engineer- 
ing (URSI) and astronomical science (IAU). The dichotomy arose from the fact that radar 
astronomy is a set of techniques (engineering) used to generate data whose interpretation 
yields answers to scientific questions. 

Just as vital to the growth of radar astronomy as meetings and journals was access to 
instruments, for without them there would be no science to discuss or to publish. The very 
availability of radar instruments capable of detecting echoes from Venus had given rise to 
planetary radar astronomy, and the field has remained a technology-driven science to the 
present. However, radar astronomers did not seek their own instruments. In league with 
the Cambridge astronomical community, Lincoln Laboratory campaigned to design and 
build a large new radar and radio astronomy research instrument. It was radio 
astronomers, not radar astronomers, who performed the entrepreneurial task of promot- 
ing the new facility and who carried radar astronomy interests with it. The same radio 
astronomers also urged opening to outside researchers the Haystack antenna built by 
Lincoln Laboratory for military communications research. 

During the 1960s, radio astronomy underwent the kind of rapid growth rate that typ- 
ifies Big Science. With fewer facilities and researchers than Australia or Britain, the lead- 
ing countries in the field, the United States saw radio astronomy balloon into Big Science 
as funding requests and antenna construction proposals increased in size and number. 
Radio astronomy thus provided an emerging Big Science onto which radar astronomers 
piggybacked their search for instruments free of military priorities and where radar 
astronomy, as recommended at the Endicptt House conference, would be "viewed as pure 
science." The potential rewards of piggybacking were great, but the price of pursuing Big 
Science patronage was equally great. In the end, the effort proved troublesome and futile. 

Needles and a Haystack 

The decade of the 1960s was the era of Big Science and the Big Dish in radio astron- 
omy. The period of large telescope construction between 1957, when thejodrell Bank 
76-meter (250-ft) telescope reached completion, and 1971, when the 100-meter (328-ft) 
radio telescope near Effelsberg (about 40 km from Bonn) began operation, has been 
dubbed "the age when big was beautiful" in radio astronomy. 27 As the first Venus experi- 
ment took place at Lincoln Laboratory in 1958, a host of new radar research instruments 
of unprecedented size were on the drawing board or under construction thanks chiefly to 
the largesse of Cold War military spending on scientific research and secondarily to the 
National Bureau of Standards and NASA. 

The NRL was breaking ground on a 183-meter (600-ft) antenna at Sugar Grove, West 
Virginia. With funding from ARPA, Cornell had completed initial design studies of a 
305-meter (1,000-ft) dish. Lincoln Laboratory had plans for a 37-meter (120-ft) antenna 
at Haystack Hill, Massachusetts, as well as a solar radar facility at El Campo, Texas, both of 
which were to be built with defense funds. 28 Stanford and SRI were soliciting military 
backing for a 244-meter (800-ft) antenna. 29 In the civilian sector, the National Bureau of 



27. Robertson, pp. 285-291, has a section called "When Big was Beautiful." 

28. The El Campo facility later was transferred from Lincoln Laboratory to the MIT Center for Space 
Research and was funded by a National Science Foundation grant. MIT, Radar Studies of the Sun and Venus: Final 
Report to the National Science Foundation under Grant No. GP-8128 (Cambridge: MIT, June 1969) . 

29. Eshleman 9 May 1994; Leadabrand and Eshleman, A Proposal for an 800-foot Radar Astronomy Telescope 
(Stanford: Stanford Research Institute, 9 October 1959), Eshleman materials. 



STURM UND DRANG 63 



Standards was building a three-station radar at its Long Branch Field Station, Illinois, and 
a huge array antenna atjicamarca, Peru, to study the ionosphere. NASA's Jet Propulsion 
Laboratory started designing a large antenna system for its Deep Space Network. In 
Europe and Australia, additional large antennas were on the drawing board or under con- 
struction. 

No less a part of the Big Dish era were the Haystack and CAMROC/NEROC anten- 
nas. Lincoln Laboratory designed and built Haystack for military communications 
research. Cambridge-area astronomers, organized as the Cambridge Radio Observatory 
Committee (CAMROC), then as the Northeast Radio Observatory Corporation 
(NEROC), campaigned to open Haystack to outside researchers. CAMROC/NEROC, 
again in collaboration with Lincoln Laboratory, also sought funding for the design and 
construction of a new large radio and radar telescope. 

Designing and building those big dishes was a nightmarish introduction to Big 
Science politics for radio astronomers. Bernard Lovell, the veteran planner and builder 
of several radio telescopes atjodrell Bank, not to mention one or two never built, in 1983 
wrote to Ed Lilley, the Harvard astronomer who headed efforts to build the new CAM- 
ROC/NEROC dish and to open Haystack to outside researchers, and asked him to sum- 
marize his experience. Lilley replied that the story presented an "excellent example of the 
mix of politics, power struggles, fiscal problems, technology and dealings with Congress, 
and, ultimately, defeat from a few scientific luminaries," and that he would "need a cabin 
overlooking a thunderous sea to stimulate the mood to undertake writing a history of the 
CAMROC/NEROC campaign.' 

The campaign began with the construction of the Haystack antenna, which replaced 
Millstone as the Lincoln Laboratory planetary radar. On 12 April 1962, Millstone stopped 
operating, so that Lincoln Laboratory could upgrade it to 1,320 MHz (23 cm; L-band) and 
increase overall system capability, as part of the Space Surveillance Techniques Program. 
Over the years, Lincoln Laboratory expanded the Millstone location. Near the Millstone 
planetary radar was the Lincoln Laboratory Communications Site, established in 1957 to 
test communication equipment. Upon completion of the tests, the antennas were torn 
down, and the site given over to construction of an X-band transmitting dish for use in 
Project West Ford, commonly known as Project Needles. A similar X-band station was built 
at Camp Parks, outside San Francisco. 31 

On 10 May 1963, Project Needles launched nearly 500 million hair-like copper wires 
into Earth orbit, thereby forming a belt of dipole antennas. Lincoln Laboratory then sent 
messages coast to coast via the orbiting copper needles between Camp Parks and 
Millstone at Westford, Massachusetts (hence the name Project West Ford). British radio 
astronomers, such as Martin Ryle and Lovell, as well as optical astronomers, objected fer- 
vently to Project Needles, and the Council of the Royal Astronomical Society formally 
protested to the U.S. President's Science Advisor. 32 Haystack was intended officially as a 
state-of-the-art radar for Project Needles. 



30. Quoted in Lovell, TheJodreU Bank Telescopes (New York: Oxford University Press, 1985) , pp. 249-250. 
Lovell has described his experiences injodrell Bank and TheJodreU Bank Telescopes. 

31. Overhage to Ferguson, 21 May 1962; Overhage to Ferguson, 28 December 1962; Overhage to 
Roscoe Wilson, 30 June 1961; J. W. Meyer, The Lincoln Laboratory General Research Program," paper pre- 
sented at the Joint Services Advisory Committee meeting, 19 April 1962, pp. 5-6; and W. H. Radford to B. A. 
Schriever, 6 May 1964, 1/24/AC 134, MITA; Lincoln Laboratory, "Millstone Hill Field Station," April 1965, 
LLLA. 

32. Overhage to Ferguson, 26 June 1963, 1/24/AC 134, MITA; Overhage and Radford, The Lincoln 
Laboratory West Ford Program: An Historical Perspective," Proceedings of the IEEE 52 (1964): 452-454; Folder 
"Project West Ford Releases and Reports," 1 .1.1 A. Much of the Proceedings of the IEEE 52 (1964): 452-606, deals 
exclusively with Project West Ford. For antagonism of radio astronomers to Project Needles, see Lovell, 
Astronomer by Chanct,, pp. 331-334; Martin Ryle and Lovell, Interference to Radio Astronomy from Belts of 
Orbiting Dipoles (Needles)," Quarterly Journal of the Royal Astronomical Society 3 (1962): 100-108; D. E. Blackwell 
and R. Wilson, "Interference to Optical Astronomy from Belts of Orbiting Dipoles (Needles)," ibid., pp. 
109-117; and H. Bondi, The West Ford Project," ibid., p. 99. 



TO SEE THE UNSEEN 



Figure 9 

Preyed Needles planned to launch nearly 500 million hair-like copper wires into Earth orbit, thereby forming a belt ofdipole 
antennas. Haystack Observatory originally was built as part of Project West Ford, which was commonly known as Project 
Needles. (Courtesy of MIT Lincoln Laboratory, Lexington, Massachusetts, photo no. P20 1-229.) 



STURM UND DRANG 65 



Project Needles and the Haystack radar exemplified the new research directions 
taken by Lincoln Laboratory. The Laboratory had pioneered three major air defense sys- 
tems: the DEW Line, the SAGE System, and the Ballistic Missile Early Warning System. 
With the formation of the MITRE Corporation in 1958, Lincoln Laboratory divested itself 
of manned bomber defense activity and engaged in new research programs that addressed 
military problems in ballistic missile re-entry systems and ballistic missile defense radars; 
military satellite communications; and the detection of underground nuclear explosions 
(Project Vela Uniform). The joint services and ARPA funded this work and supported 
Lincoln Laboratory's program of general research, which included radar and radio 
astronomy. 33 

Besides Project Needles, additional applications proposed for Haystack were track- 
ing communication satellites and radar astronomy, the former justified as an adjunct to 
communications research. The facility's X-band operating frequency ruled out meteor 
studies. Radio astronomy was also not among the initial proposed uses but emerged later 
in the earliest funding proposals submitted to the Air Force. 34 

The design of Haystack was an in-house Lincoln Laboratory effort for about a year 
and a half before the Air Force lent its financial support. The design progressed through 
several evolutionary stages. The initial March 1958 design called for a 37-meter-diameter 
(120-ft-diameter) parabolic reflector with a Cassegrainian feed, low-noise maser receivers, 
and operation in the X-band, all characteristics of the earlier West Ford antennas. The 
price tag was estimated to be about $5 million, which was too high for Air Force approval. 

The problem was to reduce the facility's cost, while designing a reflector that would 
maintain the high tolerances required for the short X-band wavelength. Exposure to wind 
and the Sun would warp the dish too much to be effective at X-band. One solution would 
have been to select a lower frequency range, say S-band, but participation in Project 
Needles dictated an X-band operating frequency. The solution was to place the antenna 
inside a radome, which not only protected the antenna from the Sun and wind, but also 
reduced the weight and power needed to drive the antenna. The radome design was sig- 
nificantly cheaper, too, lowering the estimated cost from $5 million to between $1.5 and 
$2 million. Adding the radome raised a new design issue, however, because radomes had 
never been used before at X-band. 

Lincoln Laboratory had developed a radome for L-band Millstone-type radars, but it 
could accommodate a dish no larger than 26 meters (85 ft) in diameter. To enclose the 
Haystack 37-meter (120-ft) antenna, Lincoln Laboratory engineers raised the radome 
above ground level and enlarged it from five-eighths to nine-tenths of a complete sphere. 
Electrical tests carried out in March 1959 determined that a reduction in panel thickness 
would permit the radome's use at X-band. 

In November 1959, Herb Weiss became Haystack project engineer. The following 
month, the Air Force committed financial support to die project. Lincoln Laboratory 
took bids on the radar's construction and signed a contract with North American Aviation 
(Ohio Division) on 1 December 1960. A separate Air Force contract procured the radome 
and base extension. 

Haystack was dedicated on 8 October 1964, at Tyngsboro, Massachusetts, about 30 
miles northwest of Boston, but only a half mile up the road from Millstone. Haystack was 
unique in its use of special plug-in boxes. Each box was 2.4 by 2.4 by 3.7 meters (8 by 8 by 
12 ft) and could hold up to 2 tons of equipment. One box contained a 100-kilowatt 



33. Lincoln Laboratory, The General Research Program, Report DOR-533 (Lexington: Lincoln Laboratory, 
15 June 1967), p. 1. 

34. John Harrington, The Haystack Hill Station, Technical Memorandum 78 (Lexington: Lincoln 
Laboratory, 13 October 1959), pp. 1 and 5-7, LLLA. 



66 



TO SEE THE UNSEEN 




Figure 10 

Exterior view of the Haystack Observatory in 1964, when the facility was dedicated. There, MIT and Lincoln Laboratory radar 
astronomers imaged the Moon and Venus and conducted a test of General Relativity. At the time of its dedication, Haystack 
was one of only three large antennas conducting radar astronomy research on a regular basis. (Courtesy of MIT Lincoln 
Laboratory, Lexington, Massachusetts, photo no. P10.29-783.) 

continuous-wave X-band (7,750 MHz; 4 cm) transmitter, cryogenic low-noise receivers, 
and associated microwave circuits for planetary radar research. 35 

As Haystack construction was underway, a key meeting of Harvard University 
astronomers, Donald Menzel, director of the Harvard College Observatory, Leo 
Goldberg, and Ed Lilley, took place on 24 May 1963. They came together in order to seek 
access to this new, more sensitive telescope. As a secondary objective, they sought to 
design and build a larger radio telescope in collaboration with Lincoln Laboratory. 



35. Overhage to Ferguson, 14 November 1962, Overhage to B. A. Schriever, 27 January 1964, and 
brochure, "Dedication Haystack Microwave Research Facility," 1/24/AC 134, MITA; Memorandum, J. A. Kessler 
to Radford, 30 September 1964, LLLA; "Millstone Hill Field Station;" Harrington, Haystack Hill, pp. 2-3; Weiss 
29 September 1993. For a discussion of the design and construction of Haystack, see Weiss, "The Haystack 
Microwave Research Facility," IEEE Spectrum 2 (February 1965): 50-69; Evans, Ingalls, and Pettengill, The 
Haystack Planetary Ranging Radar," in L. Efron and C. B. Solloway, eds., Scientific Applications of Radio and Radar 
Tracking in the Space Program, Technical Report 32-1475 (Pasadena: JPL, July 1970), pp. 27-36; and Weiss, W. R. 
Fanning, F. A. Folino, and R. A. Muldoon, "Design of the Haystack Antenna and Radome," in James W. Mar and 
Harold Liebowitz, eds., Structures Technology for Large Radio and Radar Telescope Systems (Cambridge: MIT Press, 
1969), pp. 151-184. 



STURM UND DRANG 67 



Lincoln Laboratory radar and radio astronomers already enjoyed relatively free access to 
Haystack, and Lincoln Laboratory radio astronomers often collaborated with their col- 
leagues at Harvard Observatory's Agassiz Station, as well as at the NRAO. The Agassiz 
Station had been training graduate students in radio astronomy for about ten years under 
a National Science Foundation grant. 

Gaining limited use of Haystack was not difficult. Lilley approached Lincoln 
Laboratory regarding use of Haystack in July 1964. In September 1965, Lincoln 
Laboratory and the Air Force reached a mutually agreeable policy on Haystack as well as 
Millstone. The Air Force encouraged use of the two facilities by scientists outside the 
Department of Defense and made Lincoln Laboratory responsible for scheduling time. 
Lincoln Laboratory had to report all outside use of Millstone and Haystack to the Air 
Force, which had final approval on all requests. Finally, outside agencies would have to pay 
an hourly fee, to be determined by Lincoln Laboratory, to defray operating and upkeep 
costs. 

At the same Harvard meeting of 24 May 1963, Lilley also suggested that Harvard, 
MIT (including Lincoln Laboratory), and the Smithsonian Astrophysical Observatory 
(SAO) jointly undertake a cooperative, regional effort to build a large dish antenna free 
of military limitations for radio astronomy research. The project sought to marry the 
strength of Lincoln Laboratory in radar astronomy and the thriving Harvard program in 
radio astronomy. 

The proposed large antenna also would serve the interests of radar astronomers. 
Although Haystack's greater power and sensitivity outclassed Millstone, Lincoln 
Laboratory radar astronomers realized that radars then under construction, namely 
Cornell's 305-meter (1,000-ft) antenna and JPL's 64-meter (210-ft) Mars Station, would 
outperform Haystack. Lincoln Laboratory radar astronomers therefore sought a tele- 
scope with Arecibo's sensitivity, but operating at a higher frequency. 36 

New enthusiasm for the construction of the large telescope ignited upon the release 
of the Whitford Report, which had endorsed the construction of large dish telescopes for 
radio astronomy. The Whitford Report grew out of Congressional reaction to the Navy's 
disastrous attempt to build an enormous steerable dish antenna in West Virginia. 



Sugar Grove 



The specter that haunted all large radio telescope dish projects was Sugar Grove. In 
the words of a report of the Comptroller General of the United States to Congress, 'The 
complexity and unique character of the Big Dish [Sugar Grove] were underestimated 
from the inception of the project." 37 As late as 1965, Harvard astronomer Ed Lilley wrote 
his colleagues, "International radio scientists still regard the U.S. Navy 600 foot 



36. "Ad Hoc Committee on Large Steerable Antenna, Report, SJuly 1963," 5/1/AC 135, Memorandum, 
Lilley to File, n.d., 10/1/AC 135, Memorandum, Lilley to Sebring and Meyer, 28 July 1964, 11/1/AC 135, 
Memorandum, 27 September 1965, "A Policy for the Use of the Millstone Hill and Haystack Facilities by 
Agencies outside the Department of Defense," 6/1/AC 135, and "Ad Hoc Committee on Large Steerable 
Antenna, Report, SJuly 1963," 5/1/AC 135, MITA; Lincoln Laboratory, General Research Program, Report DOR- 
533, p. 25; MIT Research Laboratory of Electronics, Annual Research Review and Twentieth Anniversary Program, 
10-12 May 1966, 23 March 1966, pp. 7-8, 13-14, NHOB. 

37. Comptroller General, Report to the Congress of the United States: Unnecessary Costs Incurred for the Naval 
Radio Research Station Project at Sugar Grove, West Virginia. (Washington: GPO, April 1964), p. 7. For additional 
background on the Sugar Grove dish, see Edward F. McClain, Jr., The 600-foot Radio Telescope," Scientific 
American 202 (January 1960): 45-51; James Bamford, The Puzzle Palace: A Report on America's Secret Agency (New 
York: Penguin, 1983), pp. 218-221; and Daniel S. Greenberg, "Big Dish: How Haste and Secrecy Helped Navy 
Waste $63 Million in Race To Build Huge Telescope," Science 144 (1964): 1111-1112. 



68 TO SEE THE UNSEEN 



paraboloid as a 'radio telescope' fiasco, even though the project had minuscule associa- 
tion with basic research." 38 

As early as 1948, NRL scientists devised a plan for a large steerable telescope for 
detecting and studying radio sources. By 1956, the NRL had developed an initial propos- 
al which called for a reflector 183 meters (600-ft) in diameter with accurate maneuver- 
ability and precision positioning controls. The huge dish would be able to turn a full 360 
degrees in the horizon and tilt to any angle of elevation from the zenith to the horizon. If 
completed, the 183-meter steel-and-aluminum antenna would have stood taller than the 
Washington Monument, weighed about 22,000 tons (the weight of an ocean liner) , and 
been the largest movable land-based structure ever constructed in the world. 

The Navy began breaking ground for the U.S. Naval Radio Research Station, Sugar 
Grove, West Virginia, telescope in June 1958. As construction got underway, the price tag 
rose. The initial cost estimate was $20 million, but climbed to $52.2 million in February 
1957, when the Department of Defense submitted requests for fiscal 1958 military con- 
struction funds to Congress. Later in 1957, coincidental with the launch of Sputnik, the 
Navy expanded the project concept and included certain (still) classified military surveil- 
lance tasks. The nature of those tasks, nonetheless, was an open secret. The Navy planned 
to listen to Soviet radio communications as they were reflected from the Moon, an idea 
that grew out of the lunar radar work carried out by Benjamin Yaplee's group at the NRL. 
Solar, planetary, and ionospheric radar experiments followed. 

These new tasks inflated the estimated price tag to $79 million, and the decision to 
redesign and build the telescope at the same time further ballooned the estimated cost to 
more than $200 million ($300 million in some estimates) , which was the total estimated 
cost when the Department of Defense canceled the project in July 1962. The fatal deci- 
sion to design and erect at the same time was an acknowledged "calculated risk" in order 
to save roughly three or four years of construction time. The emerging new design called 
for an antenna that was far too heavy for its support structure, which was already under 
construction. Further complicating the project was an internal turf battle between the 
Bureau of Yards and Docks and the Naval Research Laboratory. By the time the 
Department of Defense canceled Sugar Grove, the Navy had spent $42,918,914 on the 
project, but with the settlement of termination claims included, the secretary of defense 
estimated that the total expenditure for the telescope amounted to between $63 and $64 
million. 

An investigation by the comptroller general concluded that the Navy had incurred 
unnecessary costs in the construction and cancellation of the big dish. 39 The Sugar Grove 
fiasco raised serious questions about the spending of military research and development 
dollars. As Senator Hubert H. Humphrey (D-Minn.) pointed out in August 1962, Sugar 
Grove had "many of the earmarks of other research and development projects which 
turned out to be 'white elephants.'" 40 The next month, Sugar Grove came under 
Congressional scrutiny. 



38. Memorandum, Lilley, August 1965, "Comments on a Regional Radio and Radar Research Facility for 
the New England Area," p. 2-1, Box 7, UA V 630.159.10, PAHU. 

39. NRL, Careers in Space Communications (Washington: NRL, n.d.) , p. 3, NRL, Radio Astronomy and the 
600-foot Dish (Washington: NRL, n.d.), n. p., and The Big Dish," typed and edited manuscript, NRLHRC; 
Comptroller General, pp. 2-4, 6 & 11. Early specifications for Sugar Grove did not include radar experiments. 
See, for example, Specifications for the Naval Radio Facility, Sugar Grove, W. Va. (Washington: NRL, December 1957), 
and Specifications for the U.S. Naval Radio Research Station Sugar Grove, W. Va. (Washington: NRL, September 1959), 
NRLHRC. Later specifications, though, did indicate radar experiments. P. Green to Robert Page, 14 April 1960, 
and other documents, Green materials; Eshleman, "Sun Radar Experiment," in MIT, Radar Astronomy, vol. 3, lec- 
ture 15, p. 10. Fiscal irresponsibility was not the sole factor leading to the termination of the Sugar Grove pro- 
ject; the availability of satellites to perform its espionage functions was certainly another. 

40. Congressional Record, 87th Cong., 2d sess., 1962, Vol. 108, pt. 12, pp. 16175-16178. 



STURM UND DRANG 69 



The Subcommittee on Applications and Tracking and Data Acquisition of the House 
Committee on Science and Astronautics opened hearings on radio and radar astronomy 
in September 1962. The Sugar Grove fiasco motivated the hearings, at which radio 
astronomers defended their telescope projects. Witnesses discussed alternatives to large 
dishes, such as arrays, in which a number of small antennas electronically linked to each 
other acted as a single large antenna. Common to the witnesses' testimony was the asser- 
tion that the United States lagged behind Australia and Britain in radio astronomy. 41 

American backwardness in radio astronomy was widely accepted in the 1960s by 
those involved in its funding. For example, in a speech marking the dedication of the 
NRAO 43-meter (140-ft) radio telescope in 1965, Leland J. Haworth, director of the 
National Science Foundation, emphasized the Australian, British, and even Dutch lead 
over the United States in entering the field. 42 While this was neither the first nor the last 
time that a scientific community would use backwardness to argue for financial support, 
Cold War competition was not mentioned. 

As the federal agency underwriting much of the country's astronomy research, and 
as the sponsor of the NRAO, the National Science Foundation (NSF) took an avid inter- 
est in radio astronomy and its telescopes. In December 1959, well before the 
Congressional investigation of Sugar Grove, the NSF had appointed an Advisory Panel for 
Radio Telescopes to appraise current and future needs for radio telescopes. Its report, 
released in 1961 before the Sugar Grove fiasco was generally realized, did not favor the 
construction of large dish antennas. Instead, the Panel endorsed arrays using aperture 
synthesis, a new technique first developed by Martin Ryle in Britain. The endorsement of 
arrays led immediately to initial design studies of the Very Large Array (VLA) , located 
eventually in New Mexico. The NSF Panel report had more bad news for radar astronomy 
dishes. Its first resolution stated that antenna requirements for radio and radar astrono- 
my were so different, that radio astronomy antennas "should be primarily designed to 
meet the needs of passive [radio] astronomy." 43 



The Whitford Report 



Radio astronomers clamored for more telescopes. Anyone interested in building a 
new radio and/or radar telescope dish had to take into consideration the question of par- 
abolic dishes versus arrays, which were still quite experimental and untested, at least in the 
United States. The NSF was on center stage as the primary civilian funding agency for 
radio astronomy, and all design concepts and funding requests had to deal with the 
omnipresent wake of the Sugar Grove disaster. The future of large radio and radar dishes 
seemed precarious. 

Into this situation came the Committee on Government Relations of the National 
Academy of Sciences. At the suggestion of Harvard astronomer Leo Goldberg, the 
Committee created the Panel on Astronomical Facilities on 14 October 1963, in order to 
outline a planned approach to radio and optical telescope construction. Panel member- 
ship comprised prominent optical and radio astronomers; Albert E. Whitford of Lick 
Observatory served as chair. 



41 . U.S. Congress, House, Committee on Science and Astronautics, Subcommittee on Applications and 
Tracking and Data Acquisition, Report on Radio and Radar Astronomy, 87th Cong., 2d sess., 1962. 

42. "Dedication of new 140-foot radio telescope at the National Radio Astronomy Observatory, Green 
Bank, West Virginia," remarks by Dr. Leland J. Haworth, 13 October 1965, "Speeches, Leland I. Haworth," 
NSFHF. 

43. Geoffrey Keller, "Report of the Advisory Panel on Radio Telescopes," The Astrophysical Journal 134 
(1961): 927-939. 



70 TO SEE THE UNSEEN 



The Panel assembled radio astronomers at a meeting held in Washington on 1 and 
2 November 1963 in order to build a consensus. The result of the meeting and the Panel's 
deliberations was an ambitious, 10-year plan of optical and radio telescope construction. 
Nonetheless, the result of the Panel's work, known as the Whitford Report, omitted radar 
and solar astronomy. Solar astronomers protested the neglect in letter after letter. 44 

The Whitford Report specifically rejected solar radar as too costly, but completely 
neglected planetary radar astronomy. Radar astronomers did not protest. NASA's internal 
evaluation of the Whitford Report, which Nancy Roman prepared after consulting with 
those NASA committees and subcommittees responsible for developing the agency's 
astronomy program, advised NASA to continue its support of radar astronomy. 
Nonetheless, she wrote, "We do not, at present, foresee NASA support for the construc- 
tion of new radar facilities, although further experience with radar exploration of the 
solar system may modify this conclusion." In general, Roman concluded, "Support of 
astronomy is the province of the National Science Foundation," and the program of tele- 
scope construction proposed by the Whitford Report was "within the traditional province 
of the National Science Foundation which should continue to retain responsibility for 
them." Although Roman suggested that NASA deep space communications instruments 
"should incorporate potential use by radio astronomers in their design," 45 curiously she 
did not mention lending their use for radar astronomy experiments. 

Roman's evaluation summed up what became, for all practical purposes, the NASA 
position on funding radar astronomy. The construction of ground-based facilities was the 
responsibility of the NSF; NASA would fund mission-oriented research at existing facili- 
ties. The NSF embraced its role as the federal agency with primary responsibility for 
ground-based astronomy. But full implementation of the Whitford Report construction 
program required substantial increases in NSF spending on ground-based astronomy, and 
the Foundation already was the country's major underwriter of ground-based astronomy. 
In fiscal 1966, of the total federal expenditure of $46.2 million for ground-based astrono- 
my, the NSF share was $21.0 million (46 percent), compared with $9.4 million (20 per- 
cent) for NASA, $8.0 million (17 percent) for the Air Force, $4.5 million (10 percent) for 
the Navy, and $3.3 million (7 percent) for ARPA. 46 

The Whitford Report proposed to spend $224 million (about the cost of Sugar 
Grove) over 10 years on a number of regional and national facilities. It endorsed 1) a large 
array as a national facility under the NRAO (the VLA); 2) enlargement of Caltech's Owens 
Valley Observatory (another array); 3) two fully-steerable 91-meter (300-ft) dishes as 
regional facilities; 4) a design study of the largest possible steerable dish; and 5) smaller, 
special purpose instruments. 47 



44. Material in folders "Committees & Boards, Committee on Science and Public Policy, Panels, 
Astronomical Facilities, 1963," "ADM, C&B, COSPUP, Panels, Astronomical Facilities, Radio Astronomers, 
Meetings, Agenda, Nov," "Committees & Boards, Committee on Science and Public Policy, Panels, Astronomical 
Facilities, 1964," and "Committees & Boards, Committee on Science and Public Policy, Panels, Astronomical 
Facilities, Report, General, 1965," NAS; Gerard F. W. Mulders, "Astronomy Section Annual Report," 25 June 
1963, pp. 1-2, and Harold H. Lane, "Astronomy Section Annual Report," 1 July 1964, p. 1, NSFHF; Panel on 
Astronomical Facilities, Ground-Based Astronomy: A Ten-Year Program (Washington: National Academy of Sciences, 
1964), p. 57. 

45. Memorandum, Roman to Associate Administrator, Office of Space Science and Applications, 16 
March 1965, "ADM, C&B, COSPUP, Astronomical Facilities Rpt Recommendations, Assessment by NSF," NAS. 

46. Haworth to Donald F. Hornig, 5 April 1965, "Committees & Boards, Committee on Science and 
Public Policy, Panels, Astronomical Facilities, Report, Recommendations, Assessment by NSF, 1965," NAS; 
"Astronomy Section Annual Report, 1966," p. 1, "MPS Annual Reports," NSFHF. 

47. Harold H. Lane, "Astronomy Section Annual Report," 1 July 1964, p. 2, NSFHF; Ground-Based 
Astronomy, pp. 50-57. In 1955, Caltech began building a radio interferometer consisting of two 90-foot dishes at 
Owens Valley, California, funded by the U.S. Office of Naval Research. Robertson, pp. 120-121; Marshall H. 
Cohen, "The Owens Valley Radio Observatory: Early Years," Engineering and Science 57 (1994): 8-23. 



STURM UND DRANG 71 



The Whitford Report favored neither arrays nor dishes, but saw a need for both. As 
for large dishes, the Report recalled the Sugar Grove fiasco: "The design and evaluation 
of these solutions are costly and very time-consuming, as has been shown in the unsuc- 
cessful attempt at Sugar Grove to build a 600-foot [183-meter] paraboloid." The Report 
expressed the need for "a thorough-going engineering study" to ensure the construction 
of large radio telescopes and recommended spending $1 million on design studies for the 
largest feasible steerable paraboloids "at an early date." 48 



In Dish/Array 



The Whitford Report understandably excited both Harvard radio astronomers and 
Lincoln Laboratory radar astronomers with its endorsements of design studies for large 
steerable antennas and a regional 91-meter (300-ft) dish. In order to seize the opportuni- 
ties created by the Whitford Report, Harvard, MIT, and the SAO agreed to undertake a 
joint study of a large radio and radar telescope, and in August 1965, the group adopted 
the name Cambridge Radio Observatory Committee and the acronym CAMROC. 49 

In October 1965, when CAMROC drew up a research agenda for the regional tele- 
scope, planetary and lunar radar astronomy were featured uses. As Ed Lilley argued: 
"American radar astronomers have also made major contributions, but in many instances 
their work has been accomplished by 'borrowing time' on antennas which were mission 
oriented. In the Cambridge group there are radar scientists who are keenly interested in 
basic radar astronomy. They, too, need an instrument as powerful and timely as the 
Palomar 200-inch, where radar astronomy can flourish as a basic science with transmitters 
and data analysis systems developed for optimum performance on ionospheric, lunar, 
planetary, and solar problems." 50 

On 29 October 1965, Harvard, MIT, Lincoln Laboratory, and the SAO signed a 
Memorandum of Agreement, authorizing CAMROC to solicit up to $2.5 million to sup- 
port design studies for the telescope. MIT would hold, administer, and disburse the funds 
and act as CAMROC's administrative agent. CAMROC funding was to come from a vari- 
ety of sources, mostly federal. Of the estimated $2.7 million needed for fiscal 1966 and 
1967, the NSF, NASA, and the Smithsonian Institution were to award $1.57 million (58 
percent). MIT, Harvard, and private foundations (Kettering and Ford) would provide 
additional funding. 51 

The NASA money was to come through the Electronics Research Center in 
Cambridge. Unaware of NASA's evaluation of the Whitford Report, CAMROC submitted 
a grant proposal to NASA for design studies of the large steerable radio and radar 
antenna in February 1966. NASA rejected the proposal. As William Brunk, acting chief of 
Planetary Astronomy, explained, "Support for a project such as this is within the domain 
of the National Science Foundation and it is recommended that they be approached as a 
possible source of funding." NASA Deputy Administrator Robert C. Seamans, Jr., 



48. Ground-Based Astronomy, pp. 56 and 75; "Assessment of the recommendations of the Whitford 
Report, entitled 'Ground-Based Astronomy: A Ten-Year Program,'" Table V, "ADM, C&B, COSPUP, Astronomical 
Facilities Rpt Recommendations, Assessment by NSF," NAS. 

49. J. A. Stratton to S. Dillon Ripley, 14 May 1965, and Nathan M. Pusey to Stratton, 2 June 1965, 
5/1 /AC 135, and Minutes of Meeting, 26 August 1965, 14/1/AC 135, MITA. 

50. Lilley, "Comments," p. 2-1, PAHU. 

51. Memorandum, 26 October 1965, "CAMROC Support and Budget," and other documents in 
6/1/AC 135 and 12/1/AC 135, MITA. 



72 TO SEE THE UNSEEN 



repeated the message: 'The type of effort you proposed is clearly the responsibility of the 
National Science Foundation." 52 

Despite the clear and consistent reply from NASA, Joel Orlen of MIT and executive 
officer of the CAMROC Project Office (which was in charge of day-to-day activities) wrote 
to Jerome Wiesner, MIT provost, "I believe NASA should be pushed on hard to reverse this 
decision." CAMROC members came to believe that any argument made to NASA had to 
take into account the risk of offending the advocates of the JPL dish design, that is, the 
64-meter (210-ft) Mars Station. 

Wiesner wrote to Seamans, requesting that NASA reconsider the rejected proposal; 
he argued that the technology would be needed in the space effort. Seamans replied that 
NASA was studying a variety of antenna designs, including arrays, "Because we foresee, in 
an active and continuing space program, that our ground facilities will be required to 
support multiple simultaneous flight missions, it may turn out to be more effective to rely 
on a grouping of antenna systems that can be arrayed together as needed but that can also 
operate independently for independent missions." 53 

Seamans' reply threw CAMROC plans into disarray. From the beginning, the tele- 
scope was to be a large steerable dish. But arrays were gaining popularity and were 
considered a viable alternative to large radio dishes. The Whitford Report had endorsed 
both the Owens Valley array and the VLA. In 1955, Caltech began building a pair of 
27-meter (90-ft) dishes at Owens Valley, California, with money from the Office of Naval 
Research; now Caltech proposed expanding the facility. The VLA was to consist of 27 
radio telescopes mounted on railroad tracks in a Y formation whose arms were each 21 
km long. When completed, each telescope would have a diameter of 25 meters (82 ft) , 54 
Now, NASA appeared interested in arrays. But were arrays effective in radar astronomy? 

Believing that the CAMROC effort would raise questions about the merits of arrays 
versus dishes, radar astronomer and CAMROC member Gordon Pettengill tackled the 
question in a memorandum of 9 June 1966. He concluded that arrays had a number of 
advantages over a single large dish, including the ability to deliver more power to a target. 
Arrays stretched technology less, promised more reliable capability, and cost less to build. 
If some array elements were out of service for whatever reason, the deficiency would hard- 
ly affect overall performance. Moreover, if full array capability were not needed, the 
primary array could be divided into several smaller arrays and assigned to different exper- 
iments. The major design challenge of arrays, Pettengill pointed out, arose from proving 
the practicality of phasing a number of elements together. A minor drawback was the need 
for numerous low-noise receivers and antenna feeds. 55 

Lilley deflected the argument away from the merits of arrays versus dishes by 
emphasizing the use of the radome. The radome set the design apart from all other radio 
and radar antenna proposals before the NSF. If the results of the radome tests were satis- 
factory, Lilley claimed, the CAMROC studies would provide radio and radar astronomy 
with a "breakthrough in antenna technology," and the CAMROC position would be 
unique. "Unfortunately," he lamented, "only a small fraction of the radio and radar 



52. "Proposal to the National Aeronautics and Space Administration for Support of Design Studies for 
a Large Steerable Antenna for Radio and Radar Astronomy," February 1966, 55/1/AC 135, and "Project Office 
Report to CAMROC, Number 2," 30 August 1966, 5/1/AC 135, MITA; William E. Brunk to Director, Grants and 
Research Contracts, 28 July 1966, NHOB. 

53. Memorandum, Joel Orlen to Jerome Wiesner, 7 September 1966, Wiesner to Robert C. Seamans, Jr., 
3 October 1966, and Seamans to Wiesner, 15 November 1966, 55/1/AC 135, MITA. 

54. For background on the VLA, see David S. Heeschen, The Very Large Array," Sky and Telescope 49 
(1975): 344-351; and A. R. Thompson, R. G. Clark, C. M. Wade, and P. J. Napier, The Very Large Array," 
Astrophysical Journal Supplemental Series 44 (1980): 151-167. The initial theoretical development of arrays is dis- 
cussed in Bracewell, "Early Work on Imaging Theory in Radio Astronomy," pp. 167-190 in Sullivan. See also 
PA.G. Scheuer, The Development of Aperture Synthesis at Cambridge," pp. 249-265 in ibid. 

55. Memorandum, Pettengill to CAMROC Project Office File, 9 June 1966, 18/1/AC 135, MITA. 



STURM UNO DRANG 73 



professional scientists in the United States understand this, and it is unlikely that the 
National Science Foundation administrators have a clear understanding of the implica- 
tions of the CAMROC studies." 56 

Although later, in April 1967, the NSF did judge the telescope's unique design 
feature to be its radome, 57 in the meantime, the ability of the NSF to fund the CAMROC 
telescope was limited. Lilley foresaw "a dramatic expansion of demand" for federal fund- 
ing, especially from the NSF, during the summer of 1967 for large radio astronomy tele- 
scopes. 58 Nonetheless, the NSF became the largest underwriter of the CAMROC design 
studies. As of 26 April 1966, total CAMROC funds amounted to $410,000. The largest 
share, $300,000, came from an NSF grant, with additional money from Harvard 
($25,000), the SAO ($20,000), MIT Sloan Funds ($40,000), and the MIT Space Center 
($25,000) . An earlier attempt to raise money from the Kettering Foundation failed. The 
Foundation was shifting its funding away from "science" to "education," and the CAMROC 
telescope was "marginal to their interests." The likelihood of Department of Defense 
support was equally bleak. 59 

In 1966, the NSF again faced a considerable number of large radio telescope pro- 
posals, prompted this time by the large-scale spending proposed by the Whitford Report. 
In addition to the CAMROC, VLA, and Owens Valley antennas, other projects included 
"WESTROC," a joint Caltech, Stanford, and University of California at Berkeley telescope. 
WESTROC was to be a 100-meter (328-ft), fully-steerable S-band radio dish located at the 
Owens Valley site. 

In order to campaign for their telescope, CAMROC held a Conference on Radomes 
and Large Steerable Antennas on 17 and 18 June 1966. Over 70 persons attended the con- 
ference, which dealt exclusively with the proposed CAMROC dish. Participants came from 
industry (North American Aviation, Rohr Corporation, ESSCO), the NSF, the NASA 
Electronics Research Center, and the NRL, as well as from MIT, Harvard, the SAO, and 
Lincoln Laboratory. Lilley also suggested using political pressure. 60 Ultimately, CAMROC 
did apply political pressure, but not until after employing other tactics, including the 
expansion of CAMROC into a regional organization. 

NEROC 

At least as early as February 1966, CAMROC was considering ways of transforming 
itself into a regional association. The chief reason for the undertaking was to solicit funds 
for the design, construction, and operation of a regional radio and radar telescope. A 
regional base, moreover, would be useful in competing for funds against the Very Large 
Array or WESTROC. 61 



56. Memorandum, Lilley to Edward M. Purcell and Wiesner, 1 August 1966, 22/1/AC 135, MITA. 

57. "Report of the Meeting of the Advisory Committee for Mathematical and Physical Sciences," 13-14 
April 1967, p. 6, NSFHF. 

58. Memorandum, Lilley to Purcell and Wiesner, 1 August 1966, 22/1/AC 135, MITA. 

59. CAMROC Funds, 26 April 1966, 7/1/AC 135, Orlen to Wiesner, 24 November 1965, 6/1/AC 135, 
and various documents in 56/1 /AC 135, MITA. NSF Grant GP-5832 was awarded to MIT for the project "Design 
Studies for a Large Steerable Antenna for Radio and Radar Astronomy." For materials relating to the proposal, 
see 12/1/AC 135 and 57/1/AC 135, MITA. 

60. Memorandum, Lilley to Purcell and Wiesner, 1 August 1966, 22/1/AC 135, and various documents, 
49/1 /AC 135, MITA. The Institution of Electrical Engineers (London) sponsored a Conference on Large 
Steerable Aerials for Satellite Communication, Radio Astronomy, and Radar, on 6-28 June 1966. Herb Weiss, 
William Fanning, and John Ruze from Lincoln Laboratory presented five papers: "Antenna Tolerance Theory: 
A Review," "Design Considerations for a Large Fully Steerable Radio Telescope," "Performance Measurements 
on the Haystack Antenna," "Mechanical Design of the Haystack Antenna," "Performance and Design of Metal 
Space-Frame Radomes." 23/1 /AC 135, MITA. 

61. Memorandum, Orlen to Wiesner, 8 February 1966, 7/1/AC 135, MITA. > 



74 TO SEE THE UNSEEN 



CAMROC reached out to the entire Northeast to establish itself as a regional orga- 
nization with regional interests, and with justifiable claims to funding for a regional radio 
and radar telescope. One of the first steps was to choose a name, one which expressed this 
regional character. The new organization, called the Northeast Radio Observatory 
Corporation (NEROC), incorporated in Delaware on 26 June 1967. CAMROC also con- 
sidered a number of corporate arrangements, including the possibility of remaining lim- 
ited to only Cambridge schools. After lengthy discussion and analysis, CAMROC settled 
on a corporate structure that combined a "reasonable regional image" with local man- 
agement. A committee representing qualified users would determine scientific policy, 
while actual management would remain in the hands of the Cambridge group. 62 

After a detailed study of university astronomy departments in the six New England 
states, the five adjacent Midatlantic states (New York, New Jersey, Pennsylvania, Maryland, 
and Delaware), and Washington, DC, NEROC recruited its first members: Boston 
University, Brandeis University, Brown University, Dartmouth College, Harvard, MIT, the 
Polytechnic Institute of Brooklyn, the Smithsonian Institution, the State University of New 
York at Buffalo and Stony Brook, the University of Massachusetts, the University of New 
Hampshire, and Yale. 63 

Among the universities declining the NEROC invitation was Cornell, which in 1967 
managed the world's largest radio and radar antenna at Arecibo, Puerto Rico. Franklin A. 
Long, vice president for Research and Advanced Studies at Cornell, replied to the MIT 
invitation to join NEROC on 27 June 1967. Cornell radio astronomers supported the 
NEROC initiative, he explained, but they did not feel the telescope deserved top priority. 
The greatest need was for increased resolution, which the VLA promised to deliver. 
Moreover, they were "still uncertain about the relative advantages of a large steerable dish 
in the Northeast as compared to the same dish in the Southwest (or Southeast)." Having 
their own dish as well as an international agreement to use facilities overseas, Cornell was 
"concerned as to whether formal participation in NEROC would not carry the air of 
excessive Cornell greediness in this field." 64 

As CAMROC transformed itself into NEROC in 1967, the business of securing addi- 
tional funding continued. In January 1967, NEROC won a third NSF grant ($675,000) for 
telescope design studies, bringing the amount of total NSF support to $1,115,000. 
Nothing guaranteed the continuation of NSF support, however; the Foundation was faced 
with a multitude of design and construction proposals, and its budget was limited. 65 

In April 1967, the NSF Advisory Committee for Mathematical and Physical Sciences 
had four radio astronomy projects, including the CAMROC design study, under consid- 
eration with a total price tag of $120 million. Funding for all four was not available; the 
Foundation had to establish which ones to fund. The NSF had no general way to budget 
for major projects; usually, it treated requests for instrumentation, design studies, or facil- 
ities as special cases. 66 



62. "Outline of Organization and Management of Radio Observatory," 20 May 1966; untitled docu- 
ment, dated May 1966; and "Alternative Organizational Arrangements," 20 May 1966, 7/1/AC 135; Agenda, 
CAMROC meeting of 15 June 1967, 8/1 /AC 135, and documents in 61/1/AC 135, 66/1/AC 135, and 67/1/AC 
135, MITA; NEROC, Scientific Objectives of the Proposed NEROC Radio-Radar Telescope (Cambridge: NEROC, 1967), 
p. 1; Certificate of Incorporation, 22 June 1967, "NEROC," LLLA. The annotated agenda of the first meeting of 
the NEROC Board of Trustees, the minutes of that meeting, the certificate of incorporation, and the NEROC 
by-laws are in 11/64/AC 118, MITA. 

63. Documents in 8/1 /AC 135 and 65/1/AC 135, MITA; Certificate of Incorporation, 22 June 1967, 
and "Qualifications of Northeastern Institutions for CAMROC Membership," 22 March 1967, "NEROC," LLLA. 

64. Long to Wiesner, 27 June 1967, and Wiesner to James A. Perkins, 16 June 1967, 72/1/AC 135, 
MITA. 

65. John T. Wilson to Howard W.Johnson, 17January 1967, 8/1 /AC 135, and Seamans to Wiesner, 15 
November 1966, 55/1/AC 135, MITA. 

66. "Report of the Meeting of the Advisory Committee for Mathematical and Physical Sciences," 13-14 
April 1967, p. 7, NSFHF. 



STURM UNO DRANG 75 



In order to evaluate the four radio telescope proposals, the NSF appointed the Ad 
Hoc Advisory Panel for Large Radio Astronomy Facilities, called the Dicke Panel after its 
chair, Robert H. Dicke of Princeton University. By June 1967, when the Panel convened, 
the NSF had five proposals to consider: the Owens Valley array, the VLA, the Arecibo 
upgrade, the NEROC antenna, and the WESTROC dish. 

The Dicke Panel met in Washington between 24 and 28 July 1967 and listened to 
technical presentations from members of the proposing institutions. NEROC was asking 
for $28 million over five years for design and construction of a fully-steerable, radome- 
enclosed, 440-ft (134-meter) parabolic dish operating at 6,000 MHz (5-cm). Gordon 
Pettengill wrote the NEROC presentation section on radar astronomy. The NEROC tele- 
scope was not the only combined radio and radar astronomy facility looking for money. 
Thomas Gold, Frank Drake, and Rolf Dyce of Cornell University advocated renovating the 
Arecibo dish so that it could operate at 3,000 MHz (10-cm) or higher. 

Although the Dicke Panel had focused on radio astronomy, it was not blind to radar 
astronomy. The Panel recognized, for example, that "the use of radar techniques in 
astronomy has for the first time enabled man to establish direct contact with the planets 
and to set his own experimental conditions." In contrast to Pettengill's memorandum on 
radar astronomy arrays, the Dicke Panel judged that "an array cannot be used effectively 
for spectroscopic work or radar astronomy... without introducing great complications in 
the electronic system." 

Following its deliberations, the Dicke Panel submitted its report to the Director of 
the NSF on 14 August 1967. The report approved the Owens Valley array, the VLA, and 
the Arecibo upgrade. To say the least, the Dicke Panel was impressed, perhaps too 
impressed, by the potential of the spherical Arecibo dish. The Arecibo "type of antenna 
seems to show great promise for the future and should be considered along with the very 
large, fully steerable antenna for the next step forward," the Panel ruled. It urged 
appraisals of Arecibo's performance and suggested that both the WESTROC and NEROC 
proposals be deferred until more was known of the performance of spherical dishes. 67 As 
we shall see in the next chapter, the Arecibo antenna was considerably inefficient. 

The Dicke Panel report devastated NEROC plans, not to mention planetary radar 
astronomy at Lincoln Laboratory. The only radar telescope available to Lincoln 
Laboratory investigators was the Haystack antenna. The Arecibo 305-meter (1,000-ft) dish 
and JPL's 64-meter (210-ft) Mars Station, moreover, already outclassed Haystack. NEROC 
tried to salvage its antenna project. MIT physics professor Bernard F. Burke suggested that 
NEROC consider a smaller, 101-meter (330-ft) dish. "We should not be so beguiled with 
the idea of being temporarily the master of the world's biggest radio telescope," he wrote, 
"that we cannot accept an instrument that is only one of the biggest." 68 

Technical reports and symposia papers, though, continued to support the feasibility 
and desirability of the 134-meter (440-ft) design. The International Symposium on 
Structures Technology for Large Radio and Radar Telescope Systems, sponsored by MIT 
and the Office of Naval Research and held at MIT on 18-20 October 1967, saw participants 
from the United States and six other countries discussing the latest designs for large 



67. National Science Board, Approved Minutes of the Open Sessions, meeting of 8 September 1967, pp. 
113:14-113:15, National Science Board; "Draft of G. Pettengill's material for CAMROC facilities proposal," 21 
April 1967, 62/2/AC 135, and NEROC, "A Large Radio-Radar Telescope: Proposal for a Research Facility," June 
1967, 61/2/AC 135, MITA; "Report of the Ad Hoc Advisory Panel for Large Radio Astronomy Facilities," 
14 August 1967, typed manuscript, pp. 2-4, 9-10 and 13-14, NSFL. The members of the Dicke Panel were Bart 

J. Bok, Stirling A. Colgate, Rudolph Kompfner, William W. Morgan, Eugene N. Parker, Merle A. Tuve, Gart 
Westerhout, and Robert H. Dicke. 

68. Memorandum, Burke to Lilley, 6 October 1967, 8/2/AC 135, MITA. 



76 TO SEE THE UNSEEN 



telescopes in Europe, the 100-meter (328-ft) Effelsberg antenna and the proposed 122- 
meter (400-ft) dish at Jodrell Bank. 69 

Design studies for the NEROC radio and radar telescope continued. During an 18- 
month period in 1966 and 1967, an interim agreement between MIT and the Air Force 
partially underwrote the studies. Funding at Lincoln Laboratory tightened, however, and 
Herb Weiss learned that Lincoln Laboratory no longer could pay for personnel doing 
NEROC studies after 1 January 1968. The design work carried on thanks to modest sup- 
port from its Cambridge backers. The three original NEROC members, the SAO, MIT, 
and Harvard, contributed $121,241, of which MIT and Harvard gave 84 percent. 70 

The NEROC project had relied on the technical expertise and financial largesse of 
Lincoln Laboratory, plus a few not inconsequential NSF grants worth over $1.6 million. At 
this critical point, as Lincoln Laboratory "soft" money melted and the Dicke Panel advised 
deferring the NEROC telescope, getting more time on the Haystack telescope became a 
higher and urgent priority. 

HAYROC 

In October 1967, Lincoln Laboratory asked NEROC if it were interested in assuming 
responsibility for Haystack. NEROC was interested and wanted to study costs and use 
management, but without impairing progress on the design of the 134-meter (440-ft) 
antenna. As funding for the big dish design studies slowed to a trickle in 1968, NEROC 
management of Haystack began to look even more desirable. The matter was the first item 
of business at NEROC's 25 May 1968 meeting. After some discussion, NEROC unani- 
mously voted to begin negotiations with Lincoln Laboratory and to explore sources of 
financial support to turn Haystack into a regional observatory. 71 

Air Force support of Haystack paid for a single "shift," meaning five eight-hour days 
a week. NEROC radio astronomers wanted more observing hours, a second and, if possi- 
ble, a third "shift," that is, additional increments of time averaging forty hours a week. In 
response to the NEROC interest, Lincoln Laboratory offered a large portion of its current 
Haystack schedule to NEROC users at no charge, with "overtime" hours at minimal cost 
beginning January 1969. In stages, NEROC would assume responsibility for antenna man- 
agement and for securing operating funds, as available observing time increased incre- 
mentally toward a maximum schedule of four and a half shifts (three eight-hour shifts 
each day plus weekends for a total of about 2,000 hours per year for each shift) . Lincoln 
Laboratory still would be an important user of the antenna and would continue to pro- 
vide substantially to the operating budget. 

NEROC established subcommittees responsible for estimating costs, for drawing up 
mutually agreeable plans between Lincoln Laboratory and its sponsors and between 
NEROC and its sponsors, for laying out a management structure, and for pursuing fund- 
ing. Among the funding sources explored were the NASA Electronics Research Center 
and the state of Massachusetts, both of which encouraged further discussions but cau- 
tioned that eventual support, if any, would be in modest amounts. In addition, NEROC 



69. Documents in 62/1/AC 135, MITA. For the Jodrell Bank 440-foot (134-meter) MARK V telescope, 
see Lovell, The Jodrell Bank Telescopes, Chapters 5-6 and 9-11. For the Effelsberg telescope, see Otto Hachenberg, 
"The 100-meter Telescope of the Max Planck Institute for Radio Astronomy in Bonn," Proceedings of the IEEE 61 
(1973): 1288-1295, also in Mar and Liebowitz, pp. 13-27, which are the proceedings of the International 
Symposium on Structures Technology for Large Radio and Radar Telescope Systems. 

70. Weiss to Wiesner, 21 September 1967, 18/2/AC 135, and documents in 63/1/AC 135, MITA. MIT 
contributed $72,381, Harvard $30,000, and the SAO $18,860; NEROC had received $1,615,000 from the NSF. 

71. "Board of Trustees: Second Meeting of the NEROC Board of Trustees, 10/22/67," 62/1/AC 135, 
and "Board of Trustees: Third Meeting of the NEROC Board of Trustees, 5/25/68," 63/1/AC 135, MITA. 



STURM UND DRANG 77 



approached MIT, Harvard, the University of Massachusetts, and the Environmental 
Science Services Administration (for a very long baseline interferometer with their dish 
at Boulder) . The NSF was not left out of the search. 72 

Meanwhile, the NEROC 134-meter (440-ft) antenna project had languished. Now, 
though, the Smithsonian Astrophysical Observatory stepped in. The SAO had not con- 
tributed technically to the design of the big dish, nor had it contributed significantly to its 
financial support. But the SAO, through its parent organization, the Smithsonian 
Institution, could rally political support and make claims for the NEROC/Smithsonian 
telescope being a national, not a regional, facility. 

The possibility of the Smithsonian Institution obtaining Congressional authorization 
for the NEROC telescope was first summarized in a memorandum to the NEROC Board 
on 3 September 1967. During thje summer of 1968, NEROC and Smithsonian Institution 
representatives discussed the possibility of the Smithsonian Institution leading the drive 
to obtain funding for the NEROC telescope. The discussions led to an understanding, 
which included management of the project during the design, construction, and opera- 
tional phases of the facility. 73 

As a pivotal preliminary step, the Smithsonian Institution organized a meeting of 
radio and radar astronomers to marshall agreement on the need to build the NEROC tele- 
scope. If the meeting of radar and radio scientists endorsed the NEROC telescope, then 
the Smithsonian Board of Regents would be asked to approve the attempt to obtain 
Congressional authorization for it. The meeting took place at the Museum of History and 
Technology, as it was then called, at Constitution Avenue and 14th Street, NW, on 30 
November and 1 December 1968. About three dozen invited radio and radar astronomers 
and a handful of NSF and NASA officials attended, in response to an invitation from the 
Secretary of the Smithsonian Institution, S. Dillon Ripley. 

After Fred Whipple (Harvard) opened the meeting with a review of the Smithsonian 
Institution's "historical role" in astronomy, John Findlay (NRAO) explained the purpose 
and plan of the meeting and pointed out that five years after the Whitford Report, none 
of the recommended facilities had been built. Talks and discussions covered the gamut of 
telescope questions, including the Arecibo spherical dish and the issue of using arrays for 
radar astronomy. 

James Bradley, assistant secretary of the Smithsonian Institution, laid out the plan 
that his institution might follow and assuaged worries about staying on the good side of 
the NSF. MIT's Edward M. Purcell reviewed the basic design concept: a 1 34-meter-diame- 
ter (440-ft-diameter) dish, enclosed in a 171-meter (560-ft) radome, the whole costing 
about $35 million. Whipple explained that the telescope would be a national, not a 
regional, facility, and assured the gathering that the SAO would "absolutely not" dominate 
the telescope's planning and policy committee. 

On the last meeting day, Findlay sought to bring the participants together in agree- 
ment around common issues. The formal "Conclusions and Recommendation," by major- 
ity vote of the participants, declared that there was "an urgent need for a large filled- 
aperture radio-radar telescope in the United States to assist in the solution of a wide range 



72. NEROC, Proposal to the National Science Foundation for Programs in Radio and Radar Astronomy 
at the Haystack Observatory, 8 May 1970, p. V.2, LLLA; "Board of Trustees: Third Meeting of the NEROC Board 
of Trustees, 5/25/68," 63/1/AC 135; "Board of Trustees: Fourth Meeting of the NEROC Board of Trustees, 
1/18/69," 64/1/AC 135; and NEROC, Proposal to the National Science Foundation, for Research Programs in 
Radio Astronomy Using the Haystack Facility, for the period 1 July 1969 to 30 June 1970, p. 4, 11/64/AC 118, 
MITA. The proposal can be found in "Research Proposals in Radio Astronomy Using the Haystack Facility, 
7/1/69-6/30/70," 23/2/AC 135, and "Operating Expenses for the NEROC Haystack Observatory, 
7/1/69-6/30/70," 24/2/AC 135, MITA. 

73. Memorandum, Lilley to NEROC Board of Trustees, 21 November 1968, Box 1, UA V 630.159.10, 
PUHA; Documents in 64/1/AC 135, MITA. 



78 



TO SEE THE UNSEEN 



of important problems in astronomy and astrophysics." The telescope was to be operated 
as a national facility and located "primarily on the basis of scientific and technical crite- 
ria." The meeting resolved that the Smithsonian Institution should submit a proposal to 
the appropriate federal agencies and carry general responsibility for the funding, design, 
construction, and operation of the telescope. Finally, participants approved that the 
"NEROC design for a 134-meter (440-ft) telescope in a radome is close in size and gener- 
al specifications to a feasible optimum design," and endorsed it as the basis for the final 
design of the Smithsonian telescope. 74 

The meeting was an unqualified success. James Bradley wrote to Ripley after the 
meeting: "We have succeeded in gaining the support of thirty astronomers for our leg- 
islative proposal to authorize the design and construction of a large-diameter, radio-radar 
astronomical antenna." 75 The conference was only the first step in preparing to go direct- 
ly to Congress. In the following weeks, the Smithsonian Institution and NEROC assembled 
materials for the campaign. Among those materials was a publicity packet that included a 
photograph of a model of the completed dish. Herb Weiss estimated the cost of the facil- 
ity and compared the costs presented in the NSF proposal of June 1967 with projected 
costs based on June 1969 and June 1970 starting dates. 




PROPOSED 440-FOOT VERTICAL TRUSS ANTENNA IN A RADOME 



Figure 11 

Artist's drawing of the proposed NEROC 440-foot (134-meter), rr.dome-enclosed, fuUy-steerable antenna. This and other draw- 
ings and models were prepared to raise funding for the radiwadar telescope. Its radar was to operate at 5 cm (6,000 MHz or 
6 GHz), which was lower than Haystack Observatory's wavelength of 3.8 cm (7,750 MHz). (Courtesy of MIT Lincoln 
Laboratory, Lexington, Massachusetts, photo no. 259646-1.) 



74. James C. Bradley, Charles A. Lundquist, and Lilley, draft letter to all regents, 20 November 1968, and 
Memorandum, Lilley to NEROC Board of Trustees, 21 November 1968, Box 1, UA V 630.159.10, PUHA; 
"Minutes, Radio and Radar Astronomers Meeting," pp. 1-5, 8-9, 11-12, 15-18 and 24, "List of attendees and 
observers," Attachment 1, and "Conclusions and Recommendations," 61/137, SIAUSC, 1959-1972; J. W. Findlay, 
"Summary of a meeting to consider a large filled-aperture radio-radar telescope," 1 December 1968, "SAO 1968," 
217, SIAOS, SIA. 

75. Memorandum, Bradley to Ripley, 16 December 1968, "SAO 1968," 217, SIAOS, SIA. 



STURM UNO DRANG 79 



On 3 January 1969, STAG (Smithsonian Telescope Advisory Group), the radio 
astronomy advisory committee to Dillon Ripley, met at Lincoln Laboratory and reviewed 
detailed drawings of the design and the latest cost estimate. Meanwhile, the Smithsonian 
Institution Board of Regents approved requesting an initial $2 million for completing the 
NEROC design and authorized acquiring land for a site. The next step was to ask the 
Bureau of the Budget (BoB) for approval to include the $2 million request in the 
Smithsonian Institution budget for fiscal 1970. On 20 January 1969, Ripley submitted the 
proposed radio telescope legislation to the director of the BoB. 76 

Although the intention of approaching Congress directly was to circumvent the NSF 
review process, the Smithsonian Institution kept the Foundation informed. Meanwhile, in 
August 1968, NEROC submitted a proposal to the Foundation for expanded radio astron- 
omy research at Haystack. The purpose of the proposal was to increase radio observing 
time to three shifts. It also included a three-year plan for shifting management and finan- 
cial responsibility to NEROC, as well as a suggested management structure. The Haystack 
Scientific Advisory Committee, consisting of MIT and Harvard scientists, would assist the 
observatory director in approving experiments. Any qualified radio astronomer in the 
United States could request time. 77 

During what Haystack director Paul B. Sebring characterized as "the long, silent 
interval following the August 68 submission of the transfer plan" on 14 March 1969, 
Lincoln Laboratory, MIT, and NEROC concluded an interim agreement on the transfer 
of Haystack to NEROC and established the Haystack Observatory Office to evaluate and 
coordinate experiment proposals and to serve as a conduit for non-Lincoln Laboratory 
auxiliary funds for Haystack. 78 

The National Science Foundation turned the NEROC proposal over to the second 
Dicke Panel, which met in June 1969, nearly a year after NEROC submitted its proposal. 
The Panel recommended supporting Haystack radio astronomy. The blessing of the Dicke 
report turned into a one-year NSF grant effective 15 September 1969. The grant paid for 
wages, computer time, and other costs associated with adding two more shifts of observ- 
ing time. Under the conditions of the grant, moreover, the Haystack telescope was opened 
to all qualified radio astronomers in the United States, subject to the approval of the 
Haystack Scientific Advisory Committee. 79 

The orderly transition of Haystack into a civilian radio observatory appeared on 
track, until a military auditor balked at the disparity between the Department of Defense 
and NSF shares of Haystack support. The NSF had bought two-thirds of the observing 
time for $200,000, while the Air Force paid about $1.3 million for only one-third. The 



76. Ripley to Haworth, 17 March 1969, 9/2/AC 135, documents in 10/2/AC 135, 12/2/AC 135, and 
64/1/AC 135, MITA. Members of the Smithsonian Telescope Advisory Group, 18 February 1969: John W. 
Findlay, NRAO, Green Bank; Alan H. Barrett, MIT; Von R. Eshleman, Stanford; Richard M. Goldstein, JPL; Carl 
E. Heiles, UC Berkeley; John D. Krauss, Ohio State University; Frank J. Kerr, University of Maryland; A. Edward 
Lilley, Harvard; Alan T. Moffet, Caltech; Gordon H. Pettengill, Arecibo; Irwin I. Shapiro, MIT; Harold F. Weaver, 
UC Berkeley; and Gart Westerhout, University of Maryland. "NEROC Bd. of Trustees Minutes," Box 2, UA V 
630.159.10, PUHA. 

77. NEROC, Proposal to the National Science Foundation, for Research Programs in Radio Astronomy 
Using the Haystack Facility, for the period 1 July 1969 to 30 June 1970, pp. 1-2 and 4-5, 11/64/AC 118, MITA. 
The proposal also can be found in "Research Proposals in Radio Astronomy Using the Haystack Facility, 
7/1/69-6/30/70," 23/2/AC 135, and "Operating Expenses for the NEROC Haystack Observatory, 
7/1/69-6/30/70," 24/2/AC 135, MITA. The scientific advisory committee consisted of Alan H. Barrett, William 
A. Dent, A. Edward Lilley, and Irwin I. Shapiro. 

78. Memorandum, Sebring to M. U. Clauser, 21 November 1969, 12/56/AC 118, and "Haystack 
Observatory Office, Agreement Establishing the H.O.O., 3/14/69," 31/2/AC 135, MITA. 

79. "Report of the Second Meeting of the Ad Hoc Advisory Panel for Large Radio Astronomy Facilities," 
15 August 1969, p. 22, NSFL; Louis Levin to Wiesner, 12 September 1969, 18/2/AC 135, MITA; NEROC, 
Proposal to the National Science Foundation for Programs in Radio and Radar Astronomy at the Haystack 
Observatory, 8 May 1970, p. FV.3, LLLA. 



80 TO SEE THE UNSEEN 



arrangement conflicted with a Bureau of the Budget circular, and the auditor requested 
a written release from the Air Force before he would pass on the funding arrangement. 
Brig. Gen. R. A. Gilbert, Air Force Systems Command director of laboratories, refused to 
sign a written release; such a waiver, he judged, might commit the Air Force to under- 
writing Haystack through the end of fiscal 1970, a position he felt he could not take. 80 

The Mansfield Amendment cut this Gordian knot. Formally known as Section 203 of 
the Fiscal 1970 Military Procurement Authorization Act, the Mansfield Amendment com- 
pelled the Pentagon to demonstrate the mission relevance of basic research financed 
through its budget. Specifically, the Amendment stated: "None of the funds authorized to 
be appropriated by this Act may be used to carry out any research project or study unless 
such project or study has a direct or apparent relationship to a specific military function 
of operations." Sen. Mike Mansfield's goal had been to rechannel public funding for sci- 
ence through civilian rather than military agencies. 81 

The Air Force announced its intention to terminate operation of Haystack no later 
than 1 July 1970. The Mansfield Amendment was a key factor in that decision. Although 
the Air Force expressed its willingness to cooperate with the NSF in an orderly transfer, 
the decision brought chaos. With no Air Force money after 1 July 1970, Haystack was in a 
perilous financial situation. Sebring, as Haystack director, obtained NSF consent to repro- 
gram its grant funds to defray the entire cost of Haystack radio astronomy operations. A 
small grant from the Cabot Solar Energy Research Fund supplemented the NSF money. 82 

The early withdrawal of the Air Force hastened agreements on Haystack ownership, 
management, and finances. The Air Force transferred Haystack to MIT, which already 
owned the land. Haystack personnel remained employees of MIT. The NEROC Board of 
Trustees appointed the observatory director, who reported to them through the board 
chair. NEROC took responsibility for Haystack research and financing. 

To continue support of radio astronomy after 1 October 1970, NEROC submitted a 
new proposal to the NSF in May 1970. The proposal presented three alternative funding 
levels, but the NSF awarded less than that requested for a minimal program. 83 
Subsequently, the NSF annually renewed its support of Haystack radio astronomy. The suc- 
cessful transition of Haystack from military to civilian funding and monitorship ultimate- 
ly had an impact on the NEROC/SAO effort to fund the 134-meter (440-ft) telescope 
through Congress. 



The Big Dish Bill 



On 28 January 1969, Senators Clinton P. Anderson (D-N.M.), Hugh Scott (R-Pa.), 
andj. W. Fulbright (D-Ark.), all three regents of the Smithsonian Institution, introduced 
a bill in the Senate (S.705) "to authorize the Smithsonian Institution to acquire lands and 
to design a radio-radar astronomical telescope for the Smithsonian Astrophysical 
Observatory for the purpose of furthering scientific knowledge, and for other purposes." 84 



80. Brunk, Memo to the Files, 18 December 1969, NHOB. 

81. James L. Penick, Jr., Carrol W. Pursell, Jr., Morgan B. Sherwood, and Donald C. Swain, eds., The 
Politics of American Science 1939 to the Present, rev. ed. (Cambridge: The MIT Press, 1972), pp. 338-349. 

82. W. D. McElroy to Grant Hansen, 5 May 1970, 18/2/AC 135, Hurlburt to Sebring, 20 May 1970, 
18/2/AC 135, and Wiesner to Orlen, 16 July 1970, 16/2/AC 135, MITA; Hansen to Thomas O. Paine, 26 
February 1970, NHOB. 

83. NEROC, Proposal to the National Science Foundation for Programs in Radio and Radar Astronomy 
at the Haystack Observatory, 8 May 1970, p. IV. 1, 1 .1.1 A; Wiesner to Wilbur W. Bolton, Jr., 15 October 1970, 
18/2/AC 135, MITA. 

84. Documents in "Radio-Radar Telescope Legislation, 91st Congress, 7/1/69-12/31/69," 60, SIAOS, 
and "SAO 1968," 217, SIAOS, SIA; "Congress Gets 'Big Dish' Bill," Vol. 9, No. 4 The SAO News (March 1969): 
1 and 4, 24/1/AC 135, MITA. 



STURM UNO DRANG 81 



A STAG meeting of 2 April 1969 decided the site for the NEROC telescope. After set- 
tling upon a number of site criteria, STAG limited the site candidates to the continental 
United States, a decision, Fred Whipple pointed out, which led "almost inexorably to a 
final selection somewhere in the southern border states from western Texas through New 
Mexico and Arizona into California." 85 

The Smithsonian legislation, known popularly as the "Big Dish" bill, 86 requested $2 
million for the fiscal year ending 30 June 1970. The bill was read twice, then referred to 
the Senate Committee on Rules and Administration. On 17 November 1969, Morris K. 
Udall (D-Arizona) introduced the legislation in the House (H. R. 14,837), where it was 
referred to the Committee on House Administration. 

The Big Dish bill picked up approvals from NASA and the NSF. In February 1969, 
John Naugle, NASA associate administrator for Space Science and Applications, gave his 
blessing to the bill: 'The addition of such a radio-radar telescope as a national facility 
would satisfy a need for the future of radio astronomy in the United States." 87 On 17 
March 1969, Ripley asked LelandJ. Haworth, director of the NSF, for his institution's sup- 
port of the Smithsonian legislation. The NSF's reply came in the form of an invitation. 
Robert Fleischer, head of the NSF Astronomy Section, wrote that the Dicke Panel would 
reconvene, on 9-11 June 1969, and invited NEROC to prepare a 30-minute presentation 
on the current status of its radome design. 88 If the Dicke Panel again deferred or reject- 
ed the NEROC design in favor of another project, passage of the Smithsonian Institution 
bill would be jeopardized. 

Two years had passed since the first Dicke Panel met. "A need that was then urgent 
has now become critical,' the second Dicke Report declared. "While our country has 
stood still, Great Britain, the Netherlands, Germany, and India have started new, large 
radio telescopes and several are essentially complete and ready for operation." The Panel 
reaffirmed the need to upgrade the Arecibo dish and supported the Owens Valley array 
and the Very Large Array. As for the NEROC antenna, the second Dicke Panel found it 
"clear that this instrument is not only feasible, but ready for final design and construc- 
tion." The Panel recommended that "the final design and construction. ..be started 
now.. .with the utmost dispatch." The Panel suffered amnesia, too; its report claimed that 
it had "highly recommended for continuation" of the NEROC design study two years ear- 
lier. In its conclusions, the second Dicke panel declared: 'The urgent need for such a tele- 
scope is proven beyond doubt. The instrument is ready to go into the construction phase." 
Whether funded through the Smithsonian Institution or the National Science 
Foundation, "it is evident that this instrument should be operated as a national facility." 89 

The Dicke Panel report was released on 15 August 1969. Although Congress inter- 
preted the report as supporting the Big Dish, the Dicke Panel recommendations neither 
changed the playing field in Congress nor clarified the issues. After a two-hour hearing on 
10 September 1969, Rep. Frank Thompson, Jr., (D-NJ), chairman of the Subcommittee on 
Library and Memorials, deferred the Big Dish legislation. He insisted on having reports 



85. Whipple to Bradley, 3 April 1969, "Miscellaneous Correspondence and Other Material," Box 1, UA 
V 630. 159. 10, PUHA. 

86. See, for instance, "Biggest Radio-Radar Scope Asked for U.S.," Washington Evening Star, 1 April 1969, 
p. A15, in "Radar Astronomy," NHO. 

87. John E. Naugle to Richard A. Buddeke, 18 February 1969, NHOB; "Radio-Radar Telescope 
Legislation, 91st Congress, 7/1/69-12/31/69," 60, SIAOS, SIA; "SAO 1968," 217, SIAOS, SIA; "Congress Gets 
'Big Dish' Bill," pp. 1 and 4, 24/1/AC 135, MITA. 

88. Robert Fleischer to Wiesner, 20 May 1969, 18/2/AC 135, and Ripley to Haworth, 17 March 1969, 
9/2/AC 135, MITA. 

89. "Report of the Second Meeting of the Ad Hoc Advisory Panel for Large Radio Astronomy Facilities," 
15 August 1969, typed manuscript, pp. 1-3 and 15-17, NSFL. The membership of the second Dicke Panel was 
the same as the first, with the exception of Merle A. Tuve, Carnegie Institution of Washington, who was unable 
to attend. 



82 TO SEE THE UNSEEN 



from NASA, the NSF, and the Department of Defense before holding hearings. After the 
submission of the reports, hearings were set for 15 September 1969, 90 but the question was 
not settled before the end of the Congressional session. 

House hearings took place on 29 July 1970, after Rep. Thompson reintroduced the 
legislation (H. R. 13,024) on 22 July 1970. The primary hurdle facing the bill was the tight 
budget, although money was available for the war in Vietnam. As Rep. Thompson 
quipped: "Maybe if we could get this [telescope] in the Defense budget it would be all 
right, but then I would be against it." In April 1971, Lilley and the Smithsonian Institution 
in fact did consider an amendment to the Big Dish bill that would include classified Navy 
research among its duties. 91 

During the 19 July 1970 hearings, astronomers argued that the telescope was need- 
ed because the United States was behind the rest of the world in radio astronomy. At no 
point, however, did anyone defend the telescope's radar research program. The bill went 
to the Subcommittee on Library and Memorials, which unanimously voted to report the 
bill to the Committee on House Administration with the recommendation that it be 
reported to the Congress for enactment into law. 

The BoB torpedoed the Big Dish bill, however, citing the findings of a special NSF 
review committee, which had assigned higher priority to two other projects. The proposed 
expenditure, moreover, was not consistent with Nixon Administration efforts to limit fis- 
cal 1970 funding to items of the highest priority and to avoid commitments for fiscal 1971 
and beyond. Among other issues, the BoB pointed out that the bill raised basic questions 
about the appropriate roles of the Smithsonian Institution and the NSF. 92 

The Big Dish bill returned to Congress in March 1971. On 31 March 1971, Rep. 
Thompson told Dillon Ripley that the bill would go through the House 'Vith no trouble." 93 
The Greenstein Panel, however, stopped the bill. Ripley wrote to Sen. Clinton Anderson on 
23 June 1971 advising him to postpone action on the bill. The latest incarnation of the 
Dicke Panel, chaired by Jesse Greenstein, Caltech astronomy professor, was going to rec- 
ommend three facilities: the VLA, a large centimeter-wave antenna, and a large millimeter- 
wave antenna. It also was going to recommend that the VLA be started first. "In view of the 
priorities to be established by the Committee," Ripley wrote, "it does not seem wise to seek 
authorization now for the Smithsonian telescope. The three projects are all of great value 
to radio-radar astronomy and should not be put into a competition for limited Federal 
funds. If the array project is authorized on a reasonable time-scale, we look forward to a 
timely resumption of our efforts with you on the large Smithsonian telescope." 94 

The saga of the NEROC radio-radar telescope ended not in Congress, but within 
NEROC itself. Once Haystack was opened to radio astronomers from NEROC and other 
institutions, thanks to funding from the NSF, pressure to build the NEROC telescope 
eased. NEROC board members had come to realize, too, that the Big Dish bill was a lost 



90. "Radio-Radar Telescope Legislation, 91st Congress, 7/1/69-12/31/69," SIAOS, 60, SIA; "Statement 
by Herbert G. Weiss for Congressional Subcommittee Hearings, October 1969," 9/2/AC 135, MITA. 

91. Transcript of Congressional hearing of 29 July 1970, Subcommittee on Library and Memorials of 
the Committee on House Administration, pp. 381-382 and 393, "Miscellaneous Correspondence and Other 
Material," Box 1, and "Miscellaneous Correspondence and Other Material," Box 2, UA V 630.159.10, PUHA. 

92. Transcript of hearing, pp. 381-382 and 393, "Miscellaneous Correspondence and Other Material," 
Box 1; Memorandum for the record, James Bradley, 16 September 1969, and James M. Frey to Frank Thompson, 
Jr., 2 September 1969, "Miscellaneous Correspondence and Other Material," Box 2, UA V 630.159.10, PUHA; 

"SAO Radio-Radar Telescope, 1970," and Ripley to Lucien N. Nedzi, 2 April 1971, SIAOS, 61, SIA; 
Memorandum, Orlen to Wiesner, 4 February 1969, 9/2/AC 135, MITA. 

93. Ripley to Nedzi, 2 April 1971, "SAO Radio-Radar Telescope, 1971," 61, SIAOS, SIA. 

94. Ripley to Anderson, 23 June 1971, "440' Congress Suspension," Box 1, UAV630.159.10, PUHA. The 
subpanel for radio telescopes included David S. Heeschen, NRAO; Geoffrey R. Burbidge, UC La Jolla; Bernard 
F. Burke, MIT; Frank Drake, Cornell; Gordon Pettengill, MIT; and Gart Westerhout, University of Maryland. 



STURM UND DRANG 83 



cause. In addition, radio astronomy was changing; millimeter frequencies were the newest 
frontier. So at an ad hoc meeting of 25 April 1972, Ed Lilley and the other NEROC mem- 
bers voted to terminate the Big Dish project. Instead, NEROC would concentrate on an 
NSF proposal to upgrade Haystack, so that it could operate at a wavelength of three 
millimeters. 95 

In retrospect, Herb Weiss, who voted at the ad hoc meeting, reflected on the demise 
of the NEROC project: "It's very difficult to judge the absolute priorities; it's a moving ter- 
ritory. I really felt that the country made the wrong decision not to pursue NEROC. Even 
though they might have dragged it out, they might have done something, but it's such 
small money and such a great step in the right direction, and not the ultimate. I mean you 
can go beyond that, but it'll take a long time; you've got to get new materials." 96 

For planetary radar astronomy, here was a lesson in Big Science. The need for the 
NEROC telescope, the decision to design and build it, and the entrepreneurial skills and 
energy to push the project all came from radio astronomers, not radar astronomers. 
Piggybacking onto a Big Science (radio astronomy) telescope helped to overcome many 
obstacles, but in the end, the loss of control that is inherent in piggybacking cost radar 
astronomy the telescope. Also, the episode illustrated that ultimately the instrument 
needs of radio and radar astronomers can be inharmonious. 

Literally, they operate at different wavelengths. Whereas radio astronomers found a 
wavelength of three millimeters exciting, planetary radar astronomers could not operate 
at such short wavelengths. The generation of sufficient power to conduct radar experi- 
ments at millimeter wavelengths was, and remains, an insurmountable technological 
obstacle. 

The Nadir of Radar 

Three years after NEROC voted to terminate the Big Dish bill, all planetary radar 
stopped at Haystack; Lincoln Laboratory was out of the planetary radar business. The last 
Haystack planetary radar transmission traveled to Mercury on 22 March 1974. 97 The NSF 
supported radio astronomy at Haystack, but planetary radar depended on mission-orient- 
ed NASA grants. Topographical studies of the Moon and Mars supported the Apollo and 
Viking missions. In an exceptional move, when the hasty departure of the Air Force imper- 
iled the telescope's finances, NASA patched together the required amount from the 
NASA Planetary Astronomy, Viking, and Manned Spacecraft Center program budgets. 98 

The obvious explanation for the end of planetary radar at Haystack is that the 
upgraded Arecibo telescope outclassed it. Yet reality was neither so obvious nor so simple. 
The upgraded Arecibo radar, in fact, was not operational until almost a year and a half 
after Haystack carried out its last planetary radar experiment. Although the upgraded 
Arecibo telescope was far more sensitive, it could look at a target for only two hours and 
forty minutes at best. With an ability to track targets for many more hours, Haystack could 



95. Memorandum, Lilley to Bradley, 1 May 1972, "SAO Radio-Radar Telescope, 1971," 61, SIAOS, SIA. 
Those attending the meeting included: Alan Barrett, MIT; Bernard Burke, MIT; Irwin Shapiro, MIT; Paul 
Scoring, Haystack and Lincoln Laboratory; Edward Purcell, Harvard; Herbert Weiss, Lincoln Laboratory; and 
Ed Lilley, Harvard and SAO. 

A footnote to the NEROC story: a Haystack upgrade completed in January 1994 made it the premier 
United States radio observatory at 3 millimeters. An NSF review of Haystack carried out in the summer of 1994, 
only months after the NSF-funded upgrade, put funding for Haystack radio astronomy in jeopardy. Ramy A. 
Amaout, "NSF Review Puts Funding for Haystack in Jeopardy," The Tech\o\. 114, no. 18 (5 April 1994): 1 and 9. 

96. Weiss 29 September 1993. 

97. Photocopy of Haystack logbook entry provided by Richard P. Ingalls and Alan E. E. Rogers. 

98. Memorandum, HenryJ. Smith, 15 December 1969, and memorandum, Brunk to Distribution List, 
10 June 1970, NHOB. 



84 



TO SEE THE UNSEEN 



compensate for its lack of sensitivity by increasing signal integration time. Hardware alone 
was not the only reason for the end of planetary radar at Haystack. 

Haystack radar use, heavy at first, did not stop suddenly in 1974, but declined grad- 
ually over the years. In 1970, radar accounted for about a third of observing time," far 
more than at Arecibo or JPL. An optimistic NEROC proposal submitted to the NSF in 
1971 stated: "It is believed that, for the next several years, the Planetary Radar instru- 
mentation should continue to occupy the Haystack antenna for roughly 40 to 50 percent 
of the available time." 100 In fact, the actual total antenna time (exclusive of maintenance 
and improvements) for planetary radar observing fell from 17 percent in 1971 to 14 per- 
cent in 1972, then to 12 percent in 1973. 101 

Part of the problem was intense competition among radio astronomers for telescope 
time. The search for molecular spectral lines was frenetic and intensely competitive. 




Figure 12 

The, Haystack Observatory planetary radar box. Technicians preparing the box for an experiment suggest the size of the box. A 
large forklift truck raised the box into position on the telescope. (Courtesy of MIT Lincoln Laboratory, Lexington, 
Massachusetts, photo no. PI 0.29-1 785.) 



99. Sebring to Hurlburt, 27 March 1970, 18/2/AC 135, MITA. In March 1970, for example, of the 290 
hours scheduled, 90 (31 percent) were spent on radar observations. 

100. "Plan for NEROC Operation of the Haystack Research Facility as a National Radio/Radar 
Observatory, 7/1/71-6/30/73," 26/2/AC 135, MITA. 

101. NEROC, Semiannual Rej>ort of the Haystack Observatory, 15 January 1972, p. 1; ibid., 15 July 1972, p. 1; 
ibid., 15 January 1973, p. 1; and ibid., 15 August 1975, p. iii, MITA. For the 12 month period January through 
December 1973, out of 5,462.5 hours of total scientific use, planetary radar accounted for 658 hours, or about 
12 percent. "Haystack Notes June 73-Dec 74," SEBRING. 



STURM UND DRANG 85 



Although Haystack installed radio astronomy equipment on the planetary radar box in 
early 1970 to increase observing time for radio astronomers, complaints about the box 
continued. Indeed, the planetary radar box could sit on the antenna for months at a time. 
In the second half of 1972, for example, planetary radar work kept the box on the anten- 
na from 13 July to 24 September and from 9 October to 12 November. 102 As radar 
astronomer Gordon Pettengill reflected, "It wasn't convenient to make a change for a few 
hours from one box to another, and that's what really did it [Haystack] in I think." 103 

Another factor was NASA's decision to not fund research facilities. As the Air Force 
began withdrawing financial support from Haystack, NASA seemed to be a natural source 
of at least some operational funding. In his reply to the Air Force, NASA Deputy 
Administrator George M. Low explained that at NASA, "We consider, however, that with- 
in the present budgetary limitations and compared to other ongoing programs, the 
research programs that could be performed at the Haystack Facility have too low a prior- 
ity to claim NASA support of the overall operational cost of the Facility." If another agency 
were to provide general operational support, NASA would be happy to underwrite spe- 
cific, mission-oriented research, such as the topographic studies of Mars and the Moon. 104 

The Haystack radar transmitter klystron tubes, without which planetary radar could 
not be carried out, suffered from internal arcing on occasion. "At times," Haystack 
Associate Director Dick Ingalls explained, "it was hairy." 105 In 1973, Haystack asked NASA 
for a replacement klystron tube. NASA refused, accepting the risk that klystron failure 
meant the end of planetary radar research. 106 Of the two NASA missions for which 
Haystack conducted planetary radar research, Apollo and Viking, Apollo was over by 
1973. Once Haystack radar data ceased serving the needs of the Viking mission, NASA no 
longer had any mission interest in Haystack planetary radar research. 107 

Thus, temperamental klystrons, complaints from radio astronomers, the end of 
NASA mission funds, and NASA's policy of not funding facility operations all contributed 
to bring Haystack planetary radar to its nadir and demise. Despite that demise and the 
fate of the NEROC telescope, planetary radar astronomers at Lincoln Laboratory and 
MIT were not without an instrument. The future was at the Arecibo Observatory. 



102. Sebring to Hurlburt, 27 March 1970, 18/2/AC 135; NEROC, Semiannual Report of the Haystack 
Observatory, 15 August 1975, p. iii; and ibid., 15 January 1972, p. 1, MITA. Also, see the references to complaints 
by radio astronomer William A. Dent in Memorandum, Sebring to Haystack Observatory Office Members, 
2 February 1971, 44/2/AC 135, MITA. 

103. Pettengill 28 September 1993. 

104. George M. Low to Grant L. Hansen, 2 April 1970, NHOB. 

105. Ingalls 5 May 1994. 

106. Memorandum, Brunk to Joyce Cavallini, 25 July 1973, NHOB. 

107. Haystack Observatory, Final Progress Report: Radar Studies of the Planets (Westford: NEROC, 29 August 
1974). This was for NASA grant NGR-22-174-003. 



Chapter Four 

Little Science/Big Science 

Lincoln Laboratory was not the only center where planetary radar took root. Cornell 
University had its Arecibo Observatory; JPL had its Goldstone facility. At each center, 
radar astronomy developed in the shadow of military, space, radio astronomy, and iono- 
spheric Big Science. In fact, without those Big Science activities, planetary radar astrono- 
my would not have had instruments to carry out research and, in short, would not have 
existed. 

In 1961, when the first successful detections of Venus took place, virtually the sole 
funder of planetary radar astronomy in the United States was the military. The one excep- 
tion was JPL's Goldstone facility, which NASA funded. Ten years later, the NSF took over 
the role of prime underwriter of the Arecibo Observatory from ARPA, and NASA agreed 
to support a major S-band upgrade of the facility's radar. As a result, NASA became the 
de facto patron of planetary radar astronomy at Arecibo, Goldstone, and Haystack. NASA 
supported planetary radar at those three centers through a variety of financial arrange- 
ments. Only at Arecibo, however, did NASA formally agree to support a planetary radar 
facility, as well as the research conducted with it. That agreement, moreover, was an obvi- 
ous departure from its policy formulated in the wake of the Whitford Report. 

The shift from military to civilian sponsorship at Arecibo, just as in the case of 
Haystack, was not in response to the Mansfield Amendment. Under the Kennedy 
Administration, the military, mainly the Office of Naval Research, already had started 
transferring research laboratories, especially nuclear physics facilities, to the NSF. The 
budgetary reforms introduced under Defense Secretary McNamara, whose first major 
reform was to make the DoD's budget reflect the military missions for which it was respon- 
sible, probably provided the initial impetus to those transfers. 1 

The emergence of NASA as the patron of planetary radar astronomy is obvious only 
in hindsight. Throughout the 1960s, NASA refused to fund radar construction, except for 
the Deep Space Network. The NSF was the prime underwriter of astronomy facilities, but 
did not support planetary radar research. Consequently, during the 1960s, planetary 
radar astronomers depended on the kindness of Big Science, whether the radio 
astronomers at Haystack, or the NASA space programs at Goldstone, or ARPA (the mili- 
tary sponsor of Arecibo) , for its instruments. 

But in 1971, NASA broke with its established policy and paid for S-band radar 
equipment and underwrote the research conducted with it at Arecibo. The result was not 
just a new NASA policy but also the creation of a permanent institutional and financial 
home for planetary radar astronomy that the field lacked elsewhere. This unique 
arrangement came about through the complex politics of science typical of Big Science 
facilities. Complicating relations between the Arecibo Observatory and its parent organi- 
zation, as well as relations with its funding agency, were turf battles between competing 
Big Science fields (radio astronomy and ionospherics) and personality conflicts. 



1. Emilio Q. Daddario, "Needs for a National Policy," Physics Today 22 (1969): 33-38; James E. Hewes, 
Jr., From Root to McNamara: Army Organization and Administration, 1900-1963 (Washington: U.S. Army Center of 
Military History, 1975), pp. 299-315. 

87 



88 TO SEE THE UNSEEN 



The Arecibo Ionospheric Observatory 

Cornell University's 1,000-ft (305-meter) Arecibo dish began as a UHF radar man- 
aged by a civilian institution, Cornell University, but funded by the military. The (Air 
Force) Rome Air Development Center largely funded Cornell ionospheric research, and 
the original purpose of the Arecibo telescope was to conduct ionospheric research. The 
Arecibo facility started in the mind of William E. Gordon, Cornell professor of electrical 
engineering, who had devised a new incoherent scatter technique for studying electrons 
in the upper levels of the ionosphere by bombarding them with powerful radar waves. He 
worked on the technique with Cornell electrical engineering colleagues Henry Booker, 
his dissertation advisor, and Ben Nichols, both of whom shared Gordon's interest in iono- 
spheric research. A Cambridge graduate, Booker had worked in the radio section of the 
Cavendish Laboratory, and during World War II he led the theoretical division of the 
radar effort at the Telecommunications Research Establishment. 2 

In order to apply his technique, Gordon realized he needed a powerful radar, which 
he proposed to build with state-of-the-art components. Gordon also realized that the 
instrument would be costly, too costly to have a single purpose. He proposed, therefore, 
that it also do radar astronomy experiments. Henry Booker added radio astronomy, a field 
that interested him. 

Funding for the initial radar design studies, completed by Gordon, Booker, and 
Nichols in December 1958, came from the military: the Office of Naval Research, the 
Rome Air Development Center, and the Aerial Reconnaissance Laboratory, Wright Air 
Development Center, Wright-Patterson Air Force Base, Ohio. The studies outlined the 
radar parameters: a pulse radar with 2.5 megawatts of peak power and 150 kilowatts aver- 
age power (essentially the Millstone radar transmitter), a low noise temperature, and an 
operating frequency around 400 MHz (430 MHz; 70 cm in the final design). The avail- 
ability of components and antenna technical limits largely determined the operating fre- 
quency. The antenna itself was to be a parabolic dish 305 meters (1000 ft) in diameter 
fixed in a zenith-pointing position and fed from a horn on a 152-meter (500 ft) tower. 3 

Concurrent with these design studies, Bill Gordon sought funding. The budget of 
the NSF, the agency of choice for basic research, was not large enough for the project, and 
NASA was interested in building spacecraft. The National Bureau of Standards already 
had built ionospheric radars and was building a dipole array radar in Jicamarca, outside 
Lima, Peru, that incorporated Gordon's incoherent scatter technique. Its director, Ken 
Bowles, a Cornell graduate, had demonstrated the feasibility of Gordon's technique with 
a Bureau of Standards meteor radar in Illinois. 

Gordon first presented his project to ARPA in the summer of 1958. ARPA was an 
entirely new agency. Although Gordon was not aware of it at the time, ARPA's Defender 
Program was an effort to research, develop, and build a state-of-the-art defense against 



2. Gordon 28 November 1994; Benjamin Nichols, telephone conversation, 14 December 1993; 
"Cornell University Center for Radiophysics and Space Research," typed manuscript, 12 August 1959, Office of 
the Administrative Director, NAIC; Gordon, "Incoherent Scattering of Radio Waves by Free Electrons with 
Applications to Space Exploration by Radar," Proceedings of the IRE 46 (1958): 1824-1829; George Peter, Evolution 
of Receivers and Feed Systems for the Arecibo Observatory (Ithaca: NAIC, 1993), pp. 4-5; SCEL Journal Vol. S-l, no. 32 
(6 August 1953): 2, "Signal Corps Engineering Laboratory Journal/R&D Summary," HAUSACEC; Gillmor, 
"Federal Funding," p. 126. 

3. Gordon 28 November 1994; Benjamin Nichols, telephone conversation, 14 December 1993; 
Gordon, Booker, and Nichols, Design Study of a Radar to Explore the Earth's Ionosphere and Surrounding Space, 
Research Report EE 395 (Ithaca: Cornell School of Electrical Engineering, 1 December 1958), pp. 1 and 10-11; 
Gordon, Antenna Beam Swinging and the Spherical Reflector, Research Report EE 435 (Ithaca: Cornell School of 
Electrical Engineering, 1 August 1959), pp. 1 and 8; CRSR, Construction of the Department of Defense Ionospheric 
Research Facility - Final, Research Report RS 55 (Ithaca: CRSR, 30 November 1963), p. 2; Gillmor, "Federal 
Funding," p. 127. 



LITTLE SCIENCE/BIG SCIENCE 89 



Soviet missiles. Though some ARPA scientists saw the scientific value of Arecibo, ARPA's 
main interest in the project was as part of the Defender Program to track the ion trails cre- 
ated by missile exhaust. 4 

Gordon campaigned in Washington for two years. The Sugar Grove dish was a bar- 
rier to gaining approval; reviewers wanted to know why he needed to build the 305-meter 
(1000-ft) dish, when the Navy had a fully-steerable antenna under construction. Finally, 
Gordon met Ward Low of the Institute for Defense Analysis and an ARPA adviser, and 
ARPA agreed to finance the engineering and construction of the dish. The Air Force 
Office of Scientific Research (AFOSR), through the Electronics Research Directorate, Air 
Force Cambridge Research Laboratories (AFCRL), Bedford, Massachusetts, monitored 
the contract. The AFCRL now influenced the design of the telescope. Low introduced Bill 
Gordon to the AFCRL antenna group, which had been studying spherical reflectors for 
over a decade. They redesigned the fixed, zenith-looking paraboloid into a spherical 
reflector with a movable antenna feed mounted on a suspended platform. 5 

The antenna was larger than any other attempted for radar or radio astronomy, larg- 
er even than the Sugar Grove dish. The size required an unprecedented support struc- 
ture. Cornell civil engineering professors proposed placing the dish in a natural bowl in 
the earth. The proposal was practical from an engineering perspective and cut costs, 
according to preliminary studies by William McGuire and George Winter, Cornell School 
of Civil Engineering. 

Topographical, political, and scientific factors influenced the choice of a site. In the 
tropics, the planets would pass nearly overhead and into the antenna's cone of view. After 
considering sites in Hawaii, central Mexico, Cuba, Puerto Rico, and some smaller 
Caribbean islands, the search narrowed to the Island of Kauai, the Matanzas area of Cuba, 
and northern Puerto Rico. Political and import problems eliminated Cuba; Hawaii was 
too far and too remote. Puerto Rico had a favorable location, political stability, and mini- 
mum distance, as well as a karst topography full of sinkholes in which to locate the giant 
reflector. After looking at locations in Puerto Rico, Cornell chose a natural bowl in the 
mountains south of the city of Arecibo. 6 

With feasibility and location established, ARPA and Cornell signed a contract on 6 
November 1959 in which the University agreed to perform three tasks: 1) conduct design 
studies on a vertically-directed ionospheric radar probe; 2) consider ionospheric and 
other scientific uses for the instrument, then propose a priority list of the first experi- 
ments; and 3) lay out structures and buildings needed for the initial facility. 7 

Meanwhile, also in 1959, Henry Booker launched the Center for Radiophysics and 
Space Research (CRSR), an umbrella organization for mainly astronomy and electrical 
engineering faculty research, as well as management of the Arecibo facility. Booker shared 
its administration with fellow Cambridge graduate Thomas Gold. Like Booker, Gold had 



4. Gordon 28 November 1994; Nichols, telephone conversation, 14 December 1993; Jack P. Ruina, 
"Arecibo," Electronics 7 April 1961, n.p., article in publicity folder, Office of the Administrative Director, NAIC; 
CRSR, Ionospheric Research Facility, p. 2; Herbert F. York, Making Weapons, Talking Peace: A Physicist's Odyssey from 
Hiroshima to Geneva (New York: Basic Books, 1987), pp. 142-143; Gillmor, "Federal Funding," p. 126. 

5. Gordon 28 November 1994; Philip Blacksmith, "DODIRF 1000-foot Spherical Reflector Antenna," 
and Alan F. Kay, A Line Source Feed for a Spherical Reflector, Technical Report 529 (Hanscom AFB: AFCRL, 29 May 
1961), Phillips Laboratory; Roy C. Spencer, Carlyle J. Sletten, and John E. Walsh, "Correction of Spherical 
Aberration by a Phased Line Source," Proceedings of the National Electronics Conference 5 (1949): 320-333; Gillmor, 
"Federal Funding," p. 127. 

6. Gordon 28 November 1994; Gordon, "Arecibo Ionospheric Observatory," Science 146 (2 October 
1964): 26; Gordon, "Arecibo Ionospheric Observatory," p. 26; Gordon, Booker, and Nichols, pp. 12-13; Donald 

J. Belcher, "Site Locations for a Proposed Radio Telescope," Appendix C in ibidem; R. E. Mason and W. 
McGuire, The Fixed Antenna for a Large Radio Telescope: Feasibility Study and Preliminary Cost Estimate," 
Appendix B in ibidem. 

7. CRSR, Design Studies for the Arecibo Radio Observatory, Research Report RS 9 (Ithaca: CRSR, 30 June 
1960), NAIC, p. 1. 



90 TO SEE THE UNSEEN 



worked on radar during World War II, but at the Admiralty Research Establishment. After 
the war, Cambridge, the Cavendish Laboratory, and the Royal Observatory in Greenwich, 
Gold arrived in the United States in 1957 and taught astronomy at Harvard. Booker 
thought Gold ideal for running the CRSR. 8 

The CRSR staff, professors from the astronomy, electrical engineering, and physics 
departments, drew up a research program for the Arecibo telescope. Following ARPA 
guidance, they listed 20 experiments arranged in order of priority. The first three 
explored the ionosphere. Then came proposals for planetary, lunar, solar, and other radar 
work, followed by three more ionospheric experiments. The last 10 were all radio astron- 
omy experiments. The first 10, the CRSR staff concluded, were "clearly within the scope 
of the ARPA missions," but the "relation of experiments 11 through 20 [in radio astrono- 
my] to the ARPA mission is not so clear." ARPA did not appear interested in radio astron- 
omy. Well before the telescope's inauguration, however, radio astronomy had been 
assigned a major role in its scientific mission. 9 

Cornell next began building the Department of Defense Ionospheric Research 
Facility, as the telescope was named originally. Construction of the structure, antenna, 
concrete towers, and electronics were let out to over a half dozen commercial subcon- 
tractors, while the Army Corps of Engineers supervised the construction and civil engi- 
neering. The raising of the 300-ton feed platform from the bottom of the bowl, where it 
had been assembled, to its approximate final position 152 meters (500 ft) overhead, was 
an awe-inspiring sight. As Bob Price recalled, the raising of the pylons was also "Very 
impressive.. ..They had all these very strong Puerto Ricans pulling at cables. It was like 
some 1930s Mexican mural painting. Labor at its best. All coordinated pulling at these 
cables, and pouring cement at the same time, and getting the right tension on every- 
thing." 10 



8. Gold 14 December 1993; Nichols, telephone conversation, 14 December 1993; "Center for 
Radiophysics;" Annual Summary Report, Center for Radiophysics and Space Research, July 1, 1965 June 30, 1966, 

30 June 1966, p. 10; Arecibo Observatory Program Plan, October 1, 1 970 September 30, 1971, May 1971, pp. 62-63, 
AOL. 

9. CRSR, Scientific Experiments for the Arecibo Radio Observatory, Research Report RS 5 (Ithaca: CRSR, 

31 March 1960), pp. vii and 31-33; AIO, Research in Ionospheric Physics, Research Report RS 41 (Ithaca: CRSR, 30 
June 1962), p. 7. 

10. Price 27 September 1993; CRSR, Construction of the Department of Defense Ionospheric Research Facility, 
Research Report RS 22 (Ithaca: CRSR, 30 June 1961), pp. 1-2; ibid., Research Report RS 34 (Ithaca: CRSR, 
31 December 1961); ibid., Research Report RS 40 (Ithaca: CRSR, 30 June 1962), pp. 12-15; ibid., Research 
Report RS 45 (Ithaca: CRSR, 31 December 1962), pp. 1 and 11-12; various items in publicity binder, Office of 
the Administrative Director, NAIC; Thomas C. Kavanagh and David H. H. Tung, "Arecibo Radar-Radio Telescope 
Design and Construction, "Journal of the Construction Division, Proceedings of the American Satiety of Civil EngineersQl 
(May 1965): 69-98. 



LITTLE SCIENCE/BIG SCIENCE 



91 




Figure 13 

Aerial view of the Arecibo Observatory showing its location in a natural sinkhole in the hills of north central Puerto Rico. The 
antenna is so large that its can only be seen in its entirety from above. (Courtesy of National Astronomy and Ionosphere Center, 
which is operated by Cornell University under contract with the National Science Foundation.) 

After its inauguration on 1 November 1963, the Arecibo Ionospheric Observatory 
(AIO) was not just a Cornell-ARPA facility; it also became part of an international agree- 
ment for the exchange of faculty and graduate students between Cornell and the 
University of Sydney, signed in September 1964. The University of Sydney was a major, 
worldwide center for radio astronomy. The agreement gave Americans access to some of 
the most advanced radio astronomy instruments in the world, as well as some of the most 
renowned researchers. 11 

Bill Gordon directed the observatory at Arecibo. After meeting Gordon Pettengill at 
Millstone, Thomas Gold "twisted his arm" to get Pettengill to take the position of associ- 
ate director. At Lincoln Laboratory, Pettengill had carried out radar astronomy experi- 
ments, but more as a hobby. When he arrived at Arecibo in July 1963, "A totally new world 
opened up down there. This was a university-operated facility.... And there was no direct 
military work!" Pettengill devoted his entire time to planetary radar and achieved recog- 
nition in the field. 12 

What made the Arecibo world so different, apart from the lack of "military work" 
that was the bread and butter of Lincoln Laboratory, was the fact that planetary radar 
astronomy was an integral part of the scientific agenda. Arecibo's university connection 
would supply graduate student researchers. Moreover, as associate director, Pettengill 
could hire people to do planetary radar. Thus, the earliest Arecibo planetary radar 



11. CRSR Summary Report, July I, 1964 -June 30, 1965, 1 July 1965, CRSR, p. 5; Cornell-Sydney University 
Astronomy Center, 1965, p. 4, AOL; Gold and Harry Messcl, "A New Joint American-Australian Astronomy Center," 
Nature 204 (1964): 18-20. 

12. Pettengill 28 September 1993; Gold 14 December 1993. 



92 TO SEE THE UNSEEN 



astronomer was not trained in the traditional way, as a graduate student in an academic 
setting, but was hired to do planetary radar. The first such hire was Rolf B. Dyce. 

Pettengill first met Dyce years earlier, when Dyce was with the Rome Air 
Development Center, Griffiss Air Force Base, in Rome, New York. Dyce had a B.A. in 
Physics and a Ph.D. from Cornell, where he did radar studies of auroras. Dyce eventually 
landed a job with the Stanford Research Institute (SRI) at Menlo Park, California, where 
he worked on classified ionospheric and radar research, including auroral, meteor, and 
lunar studies. Dyce and Pettengill also toured Europe together and visited key radar 
research centers, including Jodrell Bank, the Dutch facility at Dwingeloo, the Chalmers 
Institute in Gothenburg, Sweden, and the Norwegian Defense Research Establishment. 
Pettengill hired Dyce in January 1964, just weeks after the Arecibo dedication in 
November 1963. 13 

Arecibo was different from Lincoln Laboratory and Haystack in many other ways, 
too, because of the relationships between Arecibo and Cornell and between Arecibo and 
Lincoln Laboratory. While MIT did not train radar astronomers to work at Lincoln 
Laboratory, Cornell sent graduate students to Arecibo to work on doctoral dissertations 
in radar astronomy. MIT students also carried out radar astronomy dissertation research 
at Arecibo. As a result, Arecibo became a training ground for future radar astronomers. 

Some of the earliest graduate student radar research was done on the Sun and 
Moon, not the planets. Vahi Petrosian, a Cornell graduate student working on a masters 
thesis, attempted some solar radar work in July and August 1964. After later attempts by 
two other graduate students, solar echo experiments were abandoned; the results were 
neither as good nor as productive as those achieved by the El Campo solar radar. 14 

On the other hand, starting in 1965, Arecibo undertook a far more vigorous and pro- 
ductive program of lunar radar research with supplementary funding from NASA, which 
hoped to use the results to help select Apollo landing sites. 15 Carrying out the lunar work 
in collaboration with Dyce and, occasionally, Pettengill was Cornell graduate student 
Thomas W. Thompson. The research formed the basis of his 1966 doctoral dissertation. 
Thompson worked briefly at Haystack, then again at Arecibo, before he found a position 
at JPL. He returned to Arecibo occasionally to make lunar radar observations. 16 



13. Dyce 22 November 1994; Pettengill 28 September 1993. 

14. AIO, Research in Ionospheric Physics, Research Report RS 61 (Ithaca: CRSR, 31 December 1964), 
pp. 46-48; ibid., Research Report RS 72 (Ithaca: CRSR, 31 January 1968), p. 127; Vahi Petrosian, Two Possible 
Methods of Detecting UHF Echoes from the Sun, Research Report RS 54 (Ithaca: CRSR, 30 September 1963), which 
was his masters thesis. His doctoral thesis, completed in June 1967, however, was on "Photoneutrino and Other 
Neutrino Processes in Astrophysics." Petrosian later went to Stanford. CRSR, "Proposal to National Science 
Foundation for Research Ionospheric Physics, Radar-Radio Astronomy, October 1, 1969 through September 30, 
1971," April 1969, pp. 138-140, Office of the Administrative Director, NAIC. 

Donald B. Campbell obtained solar continuous-wave echoes at 40 MHz (7.5 meters) during the summer 
of 1966. AIO, Research in Ionospheric Physics, Research Report RS 70 (Ithaca: CRSR, 31 January 1967), p. 75. Alan 
D. Parrish, a NASA Trainee, and Campbell made more solar observations in 1967. ibid., Research Report RS 71 
(Ithaca: CRSR, 31 July 1967), pp. 78-79; Campbell 8 December 1993. 

15. Thompson and Dyce, "Mapping of Lunar Radar Reflectivity at 70 Cm," Journal of Geophysical Research 
71 (1966): 4843-4853; Thompson, "Radar Studies of the Lunar Surface Emphasizing Factors Related to Selection 
of Landing Sites," Research Report RS 73 (Ithaca: CRSR, April 1968); Gold, CRSR Summary Report, July 1, 1964 
June 30, 1965, 1 July 1965, CRSR, p. 4; Annual Summary Report, Center for Radiophysics and Space Research, July 1, 

1966 June 30, 1967, 30 June 1967, p. 10; Annual Summary Report, Center for Radiophysics and Space Research, July 1, 
1968 June 30, 1969, 30 June 1969, p. 4; AIO, Research in Ionospheric Physics, Research Report RS 61 (Ithaca: 
CRSR, 31 December 1964), pp. 39-41. 

16. Thompson 29 November 1994; NAIC QR Q2/1970, n.p.; Thompson, "The Study of Radar- 
Scattering Behavior of Lunar Craters at 70 Cm," Ph.D. diss., Cornell, February 1966; Thompson, "Radar Studies 
of the Lunar Surface Emphasizing Factors Related to Selection of Landing Sites," Research Report RS 73 
(Ithaca: CRSR, April 1968). The lunar radar measurements were made at 40 MHz (7.5 meters) and 430 MHz (70 
cm) at the AIO. 



LITTLE SCIENCE/BIG SCIENCE 93 



The next graduate student was Raymond F. Jurgens, whose 1969 dissertation used 
Arecibo radar data to form some of the first range-Doppler images of Venus. Then came 
Donald B. Campbell, originally from Australia. Using the radar interferometric method 
developed at Haystack, and working under both Dyce and Arecibo director Frank Drake, 
Campbell began a lifelong career devoted to the radar imaging of Venus. 17 Both he and 
Jurgens later were key figures in planetary radar astronomy. 

While its relationship with Cornell turned Arecibo into a breeding ground of radar 
astronomers, its relationship with Lincoln Laboratory and Haystack, forged through the 
presence at Arecibo of Gordon Pettengill, provided entree to the software, techniques, 
and ephemerides developed by Lincoln Laboratory. Pettengill was a vital factor not only 
as associate director from 1963 to 1965, but also as Arecibo director from 1968 to 1970. 

At the heart of that relationship was the business of creating radar ephemerides. The 
standard planetary ephemerides issued by the U.S. Naval Observatory were simply not 
accurate enough for radar work, so special ephemerides computer programs had to be 
developed. In order for them to be as accurate as possible, these radar ephemerides had 
to draw on a data base of radar observations. At Lincoln Laboratory, Irwin Shapiro start- 
ed such a radar ephemerides computer program. Haystack provided a large amount of 
the ephemerides data, and so did Arecibo at the instigation of Gordon Pettengill, with a 
modest grant from NASA. Pettengill recalled the speed with which radar observational 
data arrived at Lincoln Laboratory: "I remember we used to send it back by special deliv- 
ery mail. We would mail it by six in the evening at Arecibo, and it would be delivered in 
Lexington, Massachusetts, at nine the next morning. Very efficient. Then it would be put 
into the Lincoln Laboratory ephemeris program." 18 In addition to the ephemerides, 
Lincoln Laboratory supplied Arecibo with software and techniques. As mentioned earlier, 
Don Campbell adopted the Haystack radar interferometry technique at Arecibo, and the 
special fast Fourier transform software created for the Haystack interferometer also 
migrated to Arecibo. 19 

When Pettengill left Arecibo in 1970, he returned not to Lincoln Laboratory, but to 
MIT, where he became professor of planetary physics in the Department of Earth and 
Planetary Sciences. The change from Lincoln Laboratory to MIT was as stimulating to 
Pettengill as the original move to Arecibo. He continued planetary radar research, using 
both Haystack and Arecibo. He was not alone; both Tommy Thompson and Don 
Campbell used both telescopes. 20 Moreover, Pettengill, who already had guided the radar 
astronomy dissertations researched at Arecibo, began offering a course in radar astron- 
omy at MIT and sending MIT graduate students to Arecibo to do their doctoral research. 

The fruit of this cross-fertilization between Arecibo and MIT and Lincoln Laboratory 
was that Arecibo evolved into a common research facility for both Cornell and MIT, so 
that by the time planetary radar astronomy research ended at Haystack, Arecibo already 
was in position to continue the research programs underway at Haystack. That did not 
mean, though, that the Arecibo telescope provided the same amount of observing time as 
Haystack. 

At Haystack, planetary radar astronomy accounted for a greater percentage of 
observing time than at Arecibo. Although planetary, lunar, and solar radar experiments 
occupied roughly 9 percent of Arecibo antenna time for the period December 1965 
through September 1969, only 2.4 percent of total observing time was given over to radar 



17. CRSR, "Proposal to National Science Foundation for Research Ionospheric Physics, Radar-Radio 
Astronomy, October 1, 1969 through September 30, 1971," April 1969, Office of the Administrative Director, 
NAIC, pp. 138-140; Jurgens, "A Study of the Average and Anomalous Radar Scattering from the Surface of Venus 
at 70 Cm Wavelength," Ph.D. diss., Cornell, June 1968. 

18. Pettengill 28 September 1993. 

19. Rogers 5 May 1994; Hine 12 March 1993. For a discussion of radar interferometry at Haystack and 
Arecibo, see Chapter Five. 

20. Pettengill 28 September 1993. 



94 TO SEE THE UNSEEN 



astronomy in 1970, while radar accounted for about a third of Haystack antenna time in 
the same year. 21 Moreover, as radar astronomy use of Haystack declined from 17 percent 
in 1971 to 12 percent in 1973, radar use of the Arecibo telescope increased, but not pro- 
portionally, and peaked in 1972 at 9.5 percent, somewhat lower than the lowest use at 
Haystack. The combined absolute number of total observing hours on the two telescopes 
suggests that planetary radar astronomy activity in the early 1970s was not increasing or 
even remaining stable, but was declining. It was Little Science becoming smaller. 

From ARPA to the NSF 

In November 1974, eleven years after the dedication of the Arecibo Ionospheric 
Observatory (AIO) , a second dedication ceremony took place to denote the instrument's 
upgrading to S-band. The upgrade was not achieved by simply adding higher-frequency 
equipment. The reflector surface had to be refinished, the suspended platform accom- 
modated to the new equipment, a new power supply provided, and the S-band transmit- 
ter and maser receiver designed, built, and installed. Each component of the instrument 
had to be adapted in order that the whole might function in the higher frequency range. 
For planetary radar astronomy, the upgrade essentially created a new instrument with 
entirely different and expanded capabilities. Nonetheless, however critical the upgrade 
was for radar astronomy, both radio astronomy and ionospheric research benefited sig- 
nificantly from the resurfacing and equipment improvements, too. 

The conversion of the AIO into an S-band radar telescope was a long, indirect, and 
difficult process, even if considered only as a technological feat. The conversion paralleled 
and was inextricably enmeshed in the transformation of the AIO into a National Science 
Foundation National Research Center. That transformation was set in motion by cutbacks 
in the ARPA budget, not the Mansfield Amendment. 

The realization that the S-band upgrade was possible is said to have been born in 
August 1966, during Hurricane Inez. The 100-kilometer-per-hour (62-mile-per-hour) 
winds moved the telescope less than a half inch (1.27 cm), instead of the foot (30 cm) it 
was feared. A subsequent study of the telescope structure showed that it was sufficiently 
stable to operate at wavelengths of the order of 10 cm (3,000 MHz). Optimistically, Frank 
Drake, successor to Bill Gordon as observatory director, thought that the dish could be 
resurfaced in less than two years for under $3 million. 22 

But funds were not readily available. Moreover, the annual budget allotted by ARPA 
started to shrink, from over $2 million initially to $1.8 million in the period 1965 through 
1969. Although ARPA was cutting back all research in order to support the Vietnam War, 23 



21. Sebring to Hurlburt, 27 March 1970, 18/2/AC 135, MITA; AIO, Research in Ionospheric Physics, 
Research Report RS 69 (Ithaca: CRSR, 30 June 1966), p. 87; ibid., Research Report RS 70 (Ithaca: CRSR, 31 
January 1967), pp. 124-125; ibid., Research Report RS 71 (Ithaca: CRSR, 31 July 1967), pp. 113-124; ibid., 
Research Report RS 72 (Ithaca: CRSR, 31 January 1968), pp. 125-134; ibid., Research Report RS 74 (Ithaca: 
CRSR, 31 July 1968), pp. 137-145; ibid., Research Report RS 75 (Ithaca: CRSR, 31 March 1969), p. 51; ibid., 
Research Report RS 76 (Ithaca: CRSR, 30 September 1969), p. 44; NAIC QR Q1-Q4/1970, passim. The Arecibo 
Observatory quarterly reports for the years 1971 to 1975 indicate the fraction of radar astronomy use of the 
antenna: 2.9 percent in 1971; 9.5 percent in 1972; 6.9 percent in 1973; 1.9 percent in 1974; and 7.2 percent in 
1975. At Haystack, in March 1970, for example, of the 290 hours scheduled, 90 (31 percent) were spent on radar 
observations. See Chapter 3 for Haystack radar use. 

22. Peter, p. 12; AIO, Research in Ionospheric Physics, Research Report RS 70 (Ithaca: CRSR, 31 January 
1967), p. 1. 

23. John Lannan, "An Example of Scientific Research under Scrutiny," The Sunday [Washington] Star, 30 
March 1969, p. F-3. For the AIO budget, see CRSR Summary Report, July 1, 1964 June 30, 1965, 1 July 1965, CRSR, 
p. 1; Annual Summary Refjart, Center for Radiophysics and Space Research, July 1, 1965 -June 30, 1966, 30 June 1966, 
pp. 2 and 7; ibid., July 1, 1966 June 30, 1967, 30 June 1967, pp. 8, 10 and 12; ibid., July 1, 1967 June 30, 1968, 
30 June 1968, pp. 1, 11 and 13; ibid., July 1, 1968 June 30, 1969, 30 June 1969, pp. 1 and 15. AFOSR contract 
F44-620-67-C0066 allocated $5,210,200 for the term 1 February 1967 through 30 September 1969. 



LITTLE SCIENCE/BIG SCIENCE 



95 



the Arecibo budget suffered because ARPA felt that the telescope performed below expec- 
tations. 

The antenna feed operated at only 21 percent efficiency; the dish received less than 
half the power it should have received. That was a huge dollar loss, too; the cost of build- 
ing a dish half the area would have been much less. Nonetheless, it was still an extremely 
sensitive telescope. The inefficiency of the antenna feed became a source of friction 
between Thomas Gold and Bill Gordon, who insisted that the feed could be improved, 
and between AIO management and ARPA. 24 




Figure 14 

Linear antenna feeds attached to the. suspended platform of the Arecibo Observatory. (Courtesy of National Astronomy and 
Ionosphere Center, which is of>erated by Cornell University under contract with the National Science Foundation.) 



24. Gordon 28 November 1994; Gold 14 December 1993; Campbell 7 December 1993; L. Merle 
Lalonde and Daniel E. Harris, "A High-Performance Line Source Feed for the AIO Spherical Reflector," IEEE 
Transactions on Antennas and Propagation AP-18 (January 1970): 41. 



96 TO SEE THE UNSEEN 



The line feeds were an ongoing serious problem. After a three-day visit to Arecibo in 
October 1967, BartJ. Bok, director of the Steward Observatory, Tucson, observed that the 
line feed problem "seems to be the most critical one facing the Arecibo-Cornell group." 
A number of Ithaca researchers attempted to improve the feeds. One Cornell graduate 
student considered the use of Gregorian optics, an option also studied by the AFCRL's 
Antenna Laboratory. However, not until 1988 was the first Gregorian feed tested and 
installed at Arecibo. 

Arecibo had three feed research programs going on at the same time. Only one, for 
a high-powered, 430-MHz radar feed operating at both circular polarizations, was vital to 
its radar functions. Of two competing radar feed designs, the AIO selected that of Alan 
Love of the Autonetics Corporation, a subsidiary of North American Rockwell. Love 
worked with Cornell's L. Merle Lalonde to construct an appropriate feed, which was 
installed on the antenna in early 1972. The new radar feed was a success. 25 

ARPA's funding of the AIO dropped to a great extent because of the inefficient feed. 
Too, radio astronomy at the AIO was expanding rapidly in the wake of the discovery of 
pulsars (the AIO had tremendous advantages for investigating them) , and ARPA felt more 
and more that it should support just the facility's ionospheric work, which was the only 
research relevant to Department of Defense interests. The AIO, though, hoped that ARPA 
would pay for the resurfacing and a new radar feed. 

Although the ARPA contract did not allow the AIO to seek funding from other agen- 
cies, ARPA was now receptive to the idea of sharing the AIO budget with the NSF. So with 
ARPA's blessing, Thomas Gold and Frank Drake approached the National Science 
Foundation about civilian operational money for the AIO. The AIO also submitted a 
proposal to the NSF in early 1967 for detailed engineering studies and a cost estimate to 
resurface the reflector. 26 The search for both resurfacing and operational funds thus 
proceeded concurrently and was boosted by the report of the Dicke Panel. 

Thomas Gold, Frank Drake, and Rolf Dyce pitched the Arecibo resurfacing project 
before the Dicke Panel. The Panel gave the project highest priority. As a result, Cornell 
obtained an NSF grant for a study and cost estimate of the reflector resurfacing. The AIO 
selected the Rohr Corporation, which also built JPL's Mars Station, to conduct the study. 
Rohr planned to install light aluminum panels for the reflector surface at a total cost of 
$3.5 million. 27 

The NSF, however, did not ask Congress to underwrite the resurfacing of the Arecibo 
reflector. The feed problem stood in the way. At its meeting of 16-17 October 1967, the 
NSF Astronomy Advisory Panel resolved: 28 

The NSF Advisory Panel urill be hesitant to favor the improvements of the surface of 
the Arecibo dish or the undertaking of substantial operating expenses for Arecibo until a 
successful radio astronomy feed has been constructed and made operational at frequencies 
low enough that the surface is not critical. 



25. Bok to George B. Field, "Arecibo," NSFHF; Kay, A Line Source Feed;]. Pierluissi, A Theoretical Study of 
Gregorian Radio Telescopes with Applications to the Arecibo Ionospheric Observatory, Research Report RS 57 (Ithaca: 
CRSR, 1 April 1964), NAIC; Peter, p. 18; Campbell 7 December 1993. 

26. Diary note, Hurlburt, 15 December 1967, and Long to Haworth, 27 July 1967, "Arecibo," NSFHF; 
Annual Summary Report, Center for Radiophysics and Space Research, July 1, 1965 June 30, 1966, 30 June 1966, 
pp. 12 and 18; ibid., July 1, 1966 June 30, 1967, 30 June 1967, p. 8; AIO, Research in Ionospheric Physics, Research 
Report RS 71 (Ithaca: CRSR, 31 July 1967), p. 1; Gold 14 December 1993. 

27. National Science Board, Approved Minutes of the Open Sessions, pp. 113:14-113:15, National 
Science Board; "Report of the Ad Hoc Advisory Panel for Large Radio Astronomy Facilities," 14 August 1967, 
typed manuscript, pp. 2-3, NSFL; Lalonde and Harris, p. 42; AIO, Research in Ionospheric Physics, Research Report 
RS 72 (Ithaca: CRSR, 31 January 1968), p. 4; AIO, Ibid., Research Report RS 74 (Ithaca: CRSR, 31 July 1968), 
pp. 8-9. 

28. Haworth to John Foster, 9 November 1967; Memorandum, Gerard Mulders to Haworth, Randal M. 
Robertson, and William E. Wright, 25 August 1967; and Memorandum, Mulders to Robertson, 3 January 1968, 
"Arecibo," NSFHF. 



LITTLE SCIENCE/BIG SCIENCE 97 



In short, if an adequate feed design were not feasible, investing in an expensive 
resurfacing of the reflector for operation at higher frequencies made no sense. The feed 
problem held up the resurfacing and by implication the entire S-band upgrade. 
Consequently, Cornell undertook an in-house effort to design a 327-MHz feed at its own 
expense. 

Although the reflector resurfacing project came to a temporary halt, the drive to 
secure NSF operational support succeeded in the wake of the Dicke Panel report. In July 

1967, as the Dicke Panel was meeting in Washington, Cornell Vice President for Research 
and Advanced Studies Franklin A. Long asked Leland Haworth, director of the NSF, for a 
meeting about the possibility of jointly funding the operation of the AIO with ARPA. The 
NSF and ARPA soon entered into discussions and, by late August 1967, the NSF was agree- 
able to replacing the AFOSR as the government agency monitoring the Arecibo con- 
tract. 29 This was the first step in converting the AIO into a civilian observatory. 

ARPA was prepared to underwrite the full AIO budget to the end of September 1968. 
Beginning 1 October 1968, for fiscal years 1969 through 1972, ARPA would pay for a third 
of the AIO budget, representing the portion of telescope time spent on ionospheric work. 
"It is very much hoped," the ARPA negotiator expressed, "that the entire facility will be 
identified as a National Science Foundation Observatory with ARPA as one of several 
users." 30 

In December 1967, well before passage of the Mansfield Amendment, Cornell and 
ARPA came to an agreement on the AIO contract. Cornell, NSF, and ARPA would nego- 
tiate a one-year contract for AIO operation from 1 October 1968 through 30 September 
1969. The ARPA-NSF Memorandum of Understanding, signed in late April 1969, left the 
AIO under ARPA and the AFOSR until 1 October 1969, when the NSF took over, thereby 
anticipating the effect of the Mansfield Amendment. For the fiscal year starting 1 October 

1968, each agency agreed to pay half the facility's annual budget. For the two years begin- 
ning 1 October 1969, ARPA agreed to transfer to NSF a third of the annual budget to sup- 
port just ionospheric research. ARPA did not commit any funding after 1 October 1971, 
but left the door open to the possibility. 

The Memorandum of Understanding defined ARPA's step-by-step divestment of 
Arecibo. Although ARPA initially had funded Arecibo for Project Defender, the telescope 
was never engaged in classified military research. Moreover, one clause in the 
Memorandum of Understanding specifically forbade the participation of the AIO in 
secret work: 'The Observatory shall not be used to make measurements which are them- 
selves classified nor be used as a repository for classified information." 31 The AIO was on 
the rocky road to civilian supervision and funding. 

What's In a Name? 

The transformation of the AIO into an NSF National Research Center involved two 
interconnected issues, the observatory's management structure and the status of ionos- 
pheric research, both of which were complicated by personality conflicts and turf fights 
between Big Science fields. Implicit in being a National Research Center was free access 
to the telescope for all qualified scientists. The AIO always maintained that it operated as 



29. Hurlburt diary note; Long to Peter Franken, 23 August 1967, and Long to Leland Haworth, 27 July 
1967, "Arecibo," NSFHF. 

30. Franken to William Wright, 23 August 1967, "Arecibo," NSFHF. 

31. S. J. Lukasik to Long, 12 December 1967; Memorandum of Understanding, AIO, attached to letter, 
Haworth to John Foster, 30 April 1969; and Memorandum of Understanding, AIO, attached to letter, S. E. 
Clements to Haworth, 12 May 1969, signed by Haworth and Foster, "Arecibo", NSFHF. 



98 TO SEE THE UNSEEN 



a national center, and the Cornell-Sydney agreement opened the observatory to foreign 
scientists. The real problem was that radio astronomy use of the telescope had skyrocket- 
ed, especially in contrast to ionospheric research. From December 1965 through 
September 1969, for example, ionospheric research accounted for 30 percent, while radio 
astronomy took up 50 percent of antenna time. 32 

Ionospheric research had been the reason for creating the AIO in the first place, and 
it was more interesting to the electrical engineering than to the astronomy department. 
The name of the facility changed to the Arecibo Observatory, discarding the "ionospher- 
ic" of the original name. To some individuals, the name change did not reflect the facili- 
ty's multiple research agenda, which was the intent of the change, but instead signified 
lack of interest in ionospheric work. As Gordon Pettengill explained: "We settled on that 
name early, because it encompassed the radio astronomy, radar astronomy, and ionos- 
pheric research. There was quite a group that wanted to call it the Arecibo Ionospheric 
Observatory, which was the original name under Bill Gordon." 33 Many accused Thomas 
Gold, who had fostered the expansion of radio astronomy, of thwarting ionospheric work, 
but Gold insisted that no ionospheric researchers ever were turned down. 

Perceptions outside Arecibo and Cornell confused the presumed reduction of ionos- 
pheric studies with the rift between astronomy and electrical engineering within the 
CRSR, and colored everything with the friction between Bill Gordon and Thomas Gold. 
Gold found Gordon "a little difficult, because he really wanted to cut himself off from 
Cornell, from everything completely, and I realized that if he did so, then the telescope 
would never be used for radio astronomy and radar, and it would become merely an ionos- 
pheric instrument, and that I was very opposed to, being nominally in charge of building 
such a huge wonderful instrument and then finding it's not used for what it's capable 
o f "34 Bin Gordon, for his part, stated, "If you ask me, I was mad at the time, and whatev- 
er I tell you has some personal bias built in." In short, he explained, "I thought I was 
removed from a job that I deserved to have." 35 

Frank Drake, radio astronomer and one-time Arecibo director, explained the con- 
flict rather precisely. "I had picked up enough innuendo in Gold's tone and Gordon's 
words to realize that the two of them were engaged in a bitter battle for the Arecibo turf," 
he wrote. Gold "wanted the Arecibo telescope freed to do more research in radio astron- 
omy. He was lobbying the university administration to put it under his jurisdiction." 
Gordon "could not bear to relinquish control of it." He left, however, after Gold pointed 
out to the university administration that Gordon had been off-campus far longer than the 
university bylaws allowed. "It was a fact people might have been willing to overlook, but 
once Gold seized on it, Gordon was forced to make a choice." 36 

Feelings about the friction between Gold and Gordon, as well as the perceived 
neglect of ionospheric work, also shaped how the NSF handled the AIO. The chief per- 
sonality at the NSF was Tom Jones, director of the Division of Environmental Sciences. He 
explained the situation to the NSF director in 1968: 37 



32. Maintenance and equipment improvements were 1 1 percent and radar astronomy 9 percent of 
antenna time. AIO, Research in Ionospheric Physics, Research Report RS 69 (Ithaca: CRSR, 30 June 1966), p. 87; 
Ibid., Research Report RS 70 (Ithaca: CRSR, 31 January 1967), pp. 124-125; Ibid., Research Report RS 71 (Ithaca: 
CRSR, 31 July 1967), pp. 113-124; Ibid., Research Report RS 72 (Ithaca: CRSR, 31 January 1968), pp. 125-134; 
Ibid., Research Report RS 74 (Ithaca: CRSR, 31 July 1968), pp. 137-145; Ibid., Research Report RS 75 (Ithaca: 
CRSR, 31 March 1969), p. 51; and Ibid., Research Report RS 76 (Ithaca: CRSR, 30 September 1969), p. 44. 

33. Pettengill 28 September 1993. 

34. Gold 14 December 1993. 

35. Gordon 28 November 1994. 

36. Frank Drake and Dava Sobel, Is Anyone Out There? (New York: Delacorte Press, 1992) , pp. 77 and 79. 

37. Jones to Haworth, 8 February 1968, "Arecibo," NSFHF. 



LITTLE SCIENCE/BIG SCIENCE 99 



The operation ofAIO has been tainted by a great deal of political infighting on the 
Cornell campus. Results of these confrontations included the departure from Cornell of 
Drs. W. Gordon and H. Booker, both aeronomers, who were the originators of the backscat- 
ter concept for probing the ionosphere and who saw the Arecibo venture through from the 
proposal stage right on up to its final construction and initial operation. There are indi- 
cations that, aside from accepting opportunities for professional growth, they left Cornell 
because the administrative control of AIO was removed from the director of the 
Observatory and placed in the hands of another individual on the Cornell campus. We 
do know, from conversations with aeronomers, that they do not want to give up the use of 
the Arecibo instrument. 

Jones maintained a vigil on the AIO case, as he moved from the Division of 
Environmental Sciences to the Office of National Centers, which directly oversaw the 
Arecibo Observatory. Thomas Gold found that Jones "kept expressing a sort of paranoia 
about ionospheric work, but constantly. I mean, I couldn't talk to him without getting a 
lecture that far too little ionospheric work was being done, and he couldn't support any 
funding for Arecibo if this were done, even though at the time it was doing very good work 
in radio and radar astronomy, but not enough ionosphericists wanted to go there. I could- 
n't help it!" 

According to Gold, Jones told him that he could not support funding for Arecibo if 
the reduction of ionospheric research continued. As for his relations with Bill Gordon, 
Thomas Gold insisted that it had nothing to do with ionospheric research. He and 
Gordon disagreed over the management of the observatory. According to Gold, Gordon 
wanted to operate it "in a way independent of Cornell," and he did not want to return to 
Cornell. Bill Gordon "wanted to make all the decisions as to who gets what time and all 
that," and Gold objected. 38 

Control of the observatory was the key issue dividing Gordon and Gold. The issue of 
where management of the AIO should rest, at Arecibo or at Ithaca, was precisely the con- 
cern of the NSF, too. The issue was clouded by both personality conflicts and the status of 
ionospheric research. On 27-28 February 1968, the NSF Advisory Panel for Atmospheric 
Sciences, which included Bill Gordon, issued a formal statement on the future of ionos- 
pheric research at the AIO: "As the NSF assumes increasing operational responsibility, the 
Panel strongly recommends that any management changes be made in such a way as to 
insure the availability of the AIO for experimental research in aeronomy and solar-terres- 
trial physics." Moreover, 'The Panel considers it important to establish a management 
structure for the AIO whereby scientists from institutions throughout the United States 
may use the Observatory. To accomplish this, it is suggested that the scheduling and oper- 
ating policy be established by the scientific community and implemented by the resident 
director. An appropriate way to assure representation of the scientific community would 
be to place the management of the AIO in the hands of a consortium of interested uni- 
versities." 39 

The Advisory Panel was not alone in suggesting management by a university consor- 
tium along the lines of NEROC or the NRAO. 40 However, Cornell and Gold wanted to 
retain control of the Arecibo Observatory (AO). Harry Messel, head of the University of 
Sydney School of Physics and joint director, with Gold, of the Cornell-Sydney University 



38. Gold 14 December 1993. Bill Gordon declined comment on the whole affair. Gordon 28 November 
1994. 

39. Statement of the National Science Foundation Advisory Panel for Atmospheric Sciences to the 
Director of the National Science Foundation, 21 March 1968, "Arecibo," NSFHF. 

40. See, for instance, Haworth to Long, 23 January 1968, "Arecibo," NSFHF. 



100 TO SEE THE UNSEEN 



Astronomy Center, protested to Donald F. Hornig, the special presidential assistant for sci- 
ence and technology, that any change in the AO management structure would affect the 
Cornell-Sydney arrangement, too. Despite Hornig's assurances to the contrary, the evolv- 
ing AO management structure led to the termination of the Cornell-Sydney agreement. 41 

However, the crux of the management structure question all personality and turf 
conflicts aside was separation of observatory administration from all academic depart- 
ments, like the CRSR. The NSF did not want to fund National Research Centers that were 
prisoners of an astronomy department or of any other academic unit. It was clear, though, 
that if the AO were to become a National Research Center, with a secured budget from 
the NSF, Cornell would have to draft a new management structure; otherwise, a universi- 
ty consortium might take over Cornell's managerial role. 

In March 1969, as the NSF looked toward assuming full responsibility for the AO on 
1 October 1969, the Foundation asked Cornell to prepare a proposal for the operation of 
the AO for the two-year period beginning 1 October 1969. The proposal was to discuss the 
AO management structure, "bearing in mind our opinion that a director of a National 
Center should report to a level of management significantly above that of a department 
or similar unit." 42 The April 1969 proposal outlined a management structure drafted the 
previous summer. The director of the AO reported to a policy committee, which consis- 
ted of only the university provost, the director of the CRSR (Gold), and the vice president 
for research and advanced studies. 43 

A special National Science Foundation AIO Group reviewed the proposal. Their 
major objection was the management plan: "It does not show much change from the exist- 
ing management structure at Cornell and does not appear to be suitable for a National 
Center. No member of the AIO group finds it acceptable." Specifically, the problem was 
the three-man policy committee. 'This Committee seems clearly intended by Cornell to 
be the group which runs the show. It is proposed that it be made up exclusively of Cornell 
employees resident in Ithaca. The suggestion that such a group should be considered 
'national management' has reduced the undersigned [Fregeau] to a conviction that his 
education in the art of strong language is grossly inadequate." 

The AIO Group felt that a more appropriate structure would have the observatory 
director report directly to the vice president of research, a single individual, and not a 
committee; otherwise, "the implication [is] that the committee is the AIO director's boss." 
In the judgement of the AIO Group, 'The Cornell proposal is not, in its present form, 
suitable for review by the scientific community. If it were to be sent out in this form, the 
community reaction would probably poison the beginnings of what we expect to be a fruit- 
ful venture for NSF." 44 

On 1 October 1969, when monitorship of the Arecibo contract passed to the NSF, 
Cornell reorganized the AO's management structure to conform more closely to the 
Foundation's guidance. The observatory was removed from CRSR supervision and placed 
under an Arecibo Project Office headed by Assistant Vice President for Research (Arecibo 
Affairs) Thomas Gold. 45 



41. Messel to Donald Hornig, 12June 1968, and Hornig to Messel, 9July 1968, "Arecibo, " NSFHF; Gold 
14 December 1993. 

42. Randal N. Robertson to Long, 17 March 1969, "Arecibo," NSFHF. 

43. CRSR, "Proposal to National Science Foundation for Research Ionospheric Physics, Radar-Radio 
Astronomy, October 1, 1969 through September 30, 1971," April 1969, Office of the Administrative Director, 
NAIC; advanced draft, The Management of the AIO as a National center," July, 1968, "Arecibo," NSFHF. 

44. Memorandum, J. H. Fregeau to Associate Director (Research), NSF, 28 April 1969, "Arecibo," 
NSFHF. 

45 . A nnual Summary Report, Center for Radiophysics and Space Research, July 1, 1 969 June 30, 1 970, 30 June 
1970, p. 9. 



LITTLE SCIENCE/BIG SCIENCE 101 



In the following months, Cornell and the NSF continued to consider the observa- 
tory's management structure. The result was a new organizational structure effective 
1 July 1971 that brought it more in line with other National Research Centers, and a new 
name, the "National Astronomy and Ionospheric Center" (NAIC). The name and 
acronym were intended to emulate the NRAO as a model and gave assurances of the 
importance of ionospheric research. 

In the new management structure, the title of Assistant Vice President of Research 
(Arecibo Affairs) was discontinued. Gold had quit. Those duties were given to the obser- 
vatory director, who was responsible to Cornell, through the vice president for research, 
for the overall management and operation of Arecibo. He prepared the annual budget, 
annual program plan, and long-range plans for the AO. The observatory director was to 
be located primarily in Ithaca and was also the director of the NAIC. The director of 
observatory operations, who answered to the director, had responsibility for the opera- 
don, maintenance, administration, and improvement of the facility, oversaw personnel 
and time allocations, and helped prepare the budget. He was required to be located in 
Arecibo. 46 

For the new director of observatory operations, the NAIC hired Tor Hagfors in 1971. 
His selection reassured those who worried about the status of ionospheric research. 
Hagfors had an impressive background in ionospheric (and radar) research and admin- 
istration at the Norwegian Defense Research Establishment, Stanford University, the 
Jicamarca Radio Observatory (where he was director, 1967-1969), and Lincoln 
Laboratory's Millstone Hill radar. 47 

The NSF and NASA Agreement 

As the new management structure emerged, and as the National Science Foundation 
took over the Arecibo contract, the search to fund the S-band upgrade continued. In May 
1969, the Subcommittee on Science, Research, and Development of the Committee on 
Science and Astronautics, headed by Emilio Q. Daddario (D-Conn.), recommended 
deferring the NSF request for resurfacing money. Gordon Pettengill, speaking as Arecibo 
director, pointed out that "many throughout the radio astronomy community were seri- 
ously disappointed at the failure of the Congress to authorize funds for the resurfacing of 
the AO reflector." When the Dicke Panel reconvened in June 1969 and reaffirmed the 
need for the resurfacing, they too expressed disappointment that the new reflector sur- 
face had not yet been started. 48 

A major breakthrough occurred when NASA took an interest in the project. 
Throughout the 1960s, NASA had funded only mission-oriented radar research, but not 
radar telescope construction. In January 1969, Harry H. Hess, chair of the Space Science 
Board, wrote to John Naugle, associate administrator of Space Science and Applications 
at NASA, urging NASA to fund the Arecibo radar upgrade. The cost, estimated to be $5 
million for the resurfacing plus $2 or $3 million more for the radar equipment, was "small 
in comparison with the construction of a new radar facility but would make it possible to 



46. Campbell 9 December 1993; Arecibo Observatory Program Plan, October I, 1970Sef>Umber 30, 1971, 
May 1971, pp. 35-39, Office of the Administrative Director, NAIC. 

47. Pettengill 28 September 1993; Campbell 7 December 1993; Arecibo Observatory Program Plan, 
October 1, 1971 September 30, 1972, January 1972, NAIC, pp. 25-31; Arecibo Observatory Program Plan, October 1, 
1970 September 30, 1971, May 1971, p. 63, AOL; NAIC QR Q3/1971, 9. 

48. AIO, Research in Ionospheric Physics, Research Report RS 76 (Ithaca: CRSR, 30 September 1969), p. 1; 
"Report of the Second Meeting of the Ad Hoc Advisory Panel for Large Radio Astronomy Facilities," 15 August 
1969, typed manuscript, p. 3, NSFL. 



1 02 TO SEE THE UNSEEN 



map the surface of Venus with a resolution of a few kilometers. Such a map would 
obviously be a tremendous step forward in our knowledge of the planet. The NASA con- 
tribution to the total cost of improving the Arecibo facility would be very small compared 
to the cost of obtaining the same information from some future orbiter." 49 

Hess's argument closely resembled that of Werner von Braun in an anecdote related 
by Don Campbell: "I don't know if it's apocryphal or not, but there is the story that 
Werner von Braun said, if you can get a two-kilometer resolution on Venus for $3 million, 
which is roughly what we were talking about, that it was an immense bargain, and that 
NASA should take it straight away." 50 

Indeed, NASA became interested in funding the upgrade for one major reason. The 
S-band equipment could make radar maps of the Venusian surface with a resolution of two 
to five kilometers. The space agency was interested in a one-megawatt radar operating at 
10 cm (3,000 MHz). And as NASA chief of planetary astronomy William Brunk came to 
realize, the total cost of the upgrade was a fraction of the initial cost of the facility. 51 

The country was discovering that it could not afford both guns and butter, the 
Vietnam War and the Great Society. NASA and NSF were under serious pressure to cut 
their budgets, and in December 1969, the new Republican President shut down the NASA 
Electronics Research Center in Cambridge. Budgetary austerity perhaps led NASA to sup 
port the Arecibo S-band upgrade, at a cost of a few million dollars, over the NEROC tele- 
scope, with an estimated price tag of $30 million dollars. Furthermore, given the superi- 
or transmitter power and receiver sensitivity of the upgraded Arecibo S-band radar over 
the proposed NEROC radar, NASA would be getting a better investment for its dollars. 

Budgetary belt tightening also induced NASA to realize that every planetary mission 
had to do something that could not be done from the ground, and missions would have 
to rely on ground-based results more than ever. The radar images obtainable from the 
upgraded radar would be invaluable to the exploration of the planets. Thus, the mission- 
oriented logic of NASA, combined with budgetary restraint, led to its adopting the 
Arecibo upgrade project. 52 NASA now approached the NSF. 

When NASA and NSF representatives met on 2 December 1969, the NASA budget 
for fiscal 1971 was among the topics of discussion. The space agency was going to ask for 
an extra $1 million to build a major planetary research facility as part of its Planetary 
Astronomy Program. Three candidate projects were under consideration: a 60-inch (1.5- 
meter) planetary telescope at Cerro Tololo, Chile; a large-aperture infrared telescope; 
and the Arecibo upgrade. The final choice pivoted on the NSF budget submission to the 
Bureau of the Budget and Congress. 

The NASA strategy was to pay for the resurfacing, if the NSF failed to win funds from 
Congress, and to worry about the rest of the S-band upgrade later. Brunk knew that NASA 
had to be prepared to pay for the radar equipment. Because radar equipment was "not a 
high priority item for general radio astronomy," he reasoned, "the development of a high 
power radar transmitter at a wavelength of 10 centimeters will be a low priority for NSF 
funding and must therefore be included in the NASA Planetary Astronomy budget." 53 

Soon after the NASA-NSF meeting, in February 1970, Cornell submitted a funding 
proposal for the S-band upgrade to both NASA and the NSF. The proposal asked for $3 
million over three years, with work to begin February 1971. Both the NSF and NASA fis- 
cal 1971 budget requests contained money for Arecibo. The NSF proposed to underwrite 



49. Hess to Naugle, 27 January 1969, NHOB. 

50. Campbell 7 December 1993. 

51. Brunk, Planetary Astronomy New Starts, FY 1971, n.d., NHOB. 

52. Tatarewicz, p. 98. For the creation and demise of the NASA Electronics Research Center, see Ken 
Hechler, Toward the Endless Frontier: History of the Committee on Science and Technology, 1959-1979 (Washington: 
USGO, 1980), pp. 219-231. 

53. Henry J. Smith, Memo to the files, 11 December 1969, NHOB. 



LITTLE SCIENCE/BIG SCIENCE 103 



the reflector resurfacing, while NASA budgeted for the radar equipment and its installa- 
tion. Congress approved both the NASA and NSF Arecibo S-band expenditures. The NSF 
funds were frozen, however, until a new cost estimate became available. The estimate, 
completed in November 1970, was $5.6 million. 54 

The upgrade brought together the NSF and NASA into a special relationship that 
started with joint discussions in December 1970 between William Brunk, chief of the 
NASA Planetary Astronomy Program, and Daniel Hunt, head of the NSF Office of 
National Centers and Facilities Operations. As discussions progressed, on 6 March 1971, 
NASA formally expressed its intent to enter into an agreement with the NSF for the addi- 
tion of the S-band equipment. The two agencies entered into negotiations and, on 24 June 
1971, signed a Memorandum of Agreement, which went into effect 1 July 1971. 55 

Under the agreement, the NSF funded the resurfacing and NASA the addition of a 
one megawatt S-band radar transmitter, receivers, and associated changes to the antenna 
to provide radar capability at a wavelength of ten centimeters (3,000 MHz). The project 
was to be managed under the existing NSF-Cornell contract. The NSF would serve as the 
monitoring agency, and NASA would transfer its portion of the funds to the NSF. The 
agreement deferred the issue of S-band operational costs until later, although the two 
agencies intended to share those costs proportionally. 56 

In this way, NASA came to fund radar instrument construction and committed itself 
to supporting the research performed with the instrument. This deviation from earlier 
policy was motivated by an interest in mission-oriented research, namely, to obtain radar 
images in support of space missions to the planets, particularly to Venus. The conse- 
quence was a permanent institutional and funding arrangement for planetary radar 
astronomy at Arecibo, as well as a unique instrument. 



Arecibo Joins the S-Band 



The NASA-NSF agreement, backed by Congressionally-approved funds, provided the 
legal, financial, and managerial framework for the actual upgrade work to take place. The 
upgrade began with a search for a contractor to undertake the reflector resurfacing. Two 
firms bid, the Rohr Corporation and LTV Electrosystems of Dallas, and in November 1971 
Cornell awarded the contract to LTV Electrosystems, which shortly afterward changed its 
name to E-Systems. The original spherical reflector consisted of 1/2-inch (1.3 cm) steel 
wire mesh (chicken wire) supported by heavy steel cables. Over 38,000 thin aluminum 
panels, fabricated on-site by E-Systems, replaced the chicken wire. From the beginning, 
inefficiencies and equipment failure plagued panel installation, but they were overcome, 
and the last panel was installed in November 1973. 57 



54. AIO, Proposal to NSF and NASA for Major Additions and Modifications to the Suspended Antenna Structure 
and Equipment of the Arecibo Observatory, February 1971 through February 1973, February 1970, and Daniel Hunt to 
Brunk, 11 December 1970, NHOB; National Science Board, Minutes of the Open Meetings, 132:6 and 133:7-8, 
National Science Board; NAIC QR Q3/1971, p. 13. 

55. Hunt to Brunk, 11 December 1970; NASA Deputy Associate Administrator for Space Science and 
Applications to Assistant Administrator, Office of DoD and Interagency Affairs, 6 March 1971; Memorandum, 
Director of Planetary Programs, Office of Space Science and Applications, NASA, to Associate Administrator for 
Office of Tracking and Data Acquisition, 20 May 1971; and Memorandum of Agreement between NASA and the 
NSF for the Addition of a High-Power S-Band Radar Capability and Associated Additions and Modifications to 
the Suspended Antenna Structure of the NAIC at Arecibo, 24 June 1971, NHOB. 

56. Memorandum of Agreement between NASA and the NSF for the Addition of a High-Power S-Band 
Radar Capability and Associated Additions and Modifications to the Suspended Antenna Structure of the NAIC 
at Arecibo, 24 June 1971, NHOB; "High Power Transmitter to Boost Arecibo Radar Capability," NSF press 
release, 17 August 1971, "Radar Astronomy," NHO. 

57. NAIC QR Ql/1971, p. 5; Q2/1971, p. 6; Q3/1971, p. 6; Q4/1971, p. 7; Ql/1972, p. 10; Q2/1972, 
p. 13; Q3/1972, p. 11; and Ql/1973, p. 13; National Science Board, Minutes of the Open Meetings, 144:4-5, 
National Science Board. 



1 04 TO SEE THE UNSEEN 



Concurrently, the NAIC oversaw the design and construction of the S-band radar 
transmitter, receivers, and associated equipment; the necessary modifications to the sus- 
pended feed platform; and construction of a new carriage house to hold the S-band 
equipment. Ammann & Whitney, a well-known structural engineering consulting firm, 
reported on the suspended structure and reflector cable anchorages as well as on the fea- 
sibility of upgrading the suspended structure. They found no basic deficiencies in the 
structure that would make upgrading impractical or inadvisable. 58 

In order to develop specific transmitter characteristics that met scientific goals, yet 
represented realistic state-of-the-art feasibility, NAIC staff discussed its design with experi- 
enced radar astronomers and with experts from Varian Associates, Raytheon, and 
Continental Electronics. The operating frequency, 2380 MHz (12.6 cm), appeared to be 
the optimum choice for both radar and radio astronomy and was close to the JPL plane- 
tary radar frequency (2388 MHz; 12.6 cm). 59 

Originally, the transmitter was to produce 800 kilowatts using two klystrons. The 
NAIC based the decision on the experience of JPL Goldstone, where a single klystron pro- 
duced 400 kilowatts of average continuous-wave power at 2388 MHz. Although Varian was 
developing a one megawatt continuous-wave klystron, the advantages of proven reliability 
and ready availability of spares militated against using a single, experimental one- 
megawatt klystron. Finally, after extensive discussion with representatives of NASA and the 
NSF, the NAIC reduced the transmitter power requirement to 450 kilowatts, thereby low- 
ering costs "without impacting upon scientific goals of the program." In contrast, the orig- 
inal UHF radar transmitter produced only 150 kilowatts of average power. 60 

The experience of JPL in operating at S-band proved invaluable to the Arecibo radar 
upgrade. In addition to providing expert advice to the NAIC staff, a former JPL employ- 
ee reviewed technical matters for the NASA technical monitor. The maser receivers, more- 
over, were excess Deep Space Network equipment. The agreement between the NAIC and 
JPL for the transfer of the masers noted that JPL was "a pioneer in the development of 
maser systems," and that "no commercial firms have the required capability, experience 
and expertise to produce an S-band maser system that would be operational at 2.38 
GHz."" 

The renovated reflector was dedicated on 15-16 November 1974. After delivery of 
the keynote speech, Rep. John W. Davis (D-Ga.) gave the signal for the transmission of 
The Arecibo Message, 1974, an attempt to communicate with extraterrestrial civilizations. 
The radar upgrade, however, was not yet completed and would not be entirely ready until 
the following year. 62 

Yet, shortly after the resurfacing dedication, Gordon Pettengill (Arecibo) and 
Richard Goldstein (JPL) used the S-band transmitter to bounce signals off the rings of 
Saturn. Because the Arecibo maser receiver was not yet installed, Arecibo sent and JPL's 
Mars Station received. The bistatic experiment worked, despite line feed and turbine gen- 
erator problems at Arecibo. 



58. AIO, Proposal to NSF and NASA for Major Additions and Modifications to the Suspended Antenna Structure 
and Equipment of the Arecibo Observatory, February 1971 through February 1973, February 1970, pp. 7-8, 11-15, 
NHOB; NAIC QR Q3/1972, pp. 11-12. 

59. NAIC QR Q4/1971, p. 8; and Q2/1972, p. 13. 

60. Campbell 8 December 1993; NAIC QR Q2/1970, p. 4, Q4/1970, p. 9, Ql/1972, p. 12, Q3/1972, p. 
12, and Ql/1973, p. 14; AIO, Proposal to NSF and NASA for Major Additions and Modifications to the Suspended 
Antenna Structure and Equipment of the Arecibo Observatory, February 1971 through February 1973, February 1970, pp. 
14-15, NHOB; AIO dedication brochure, no page numbers, Cornell, 1974, NHOB. 

61. Brunk to Claude Kellett, 18 April 1973, NHOB; Jack W. Lowe to W. E. Porter, 29 March 1977, Office 
of the Administrative Director, NAIC; NAIC QR Ql/1972, p. 1 1; Peter, p. 13. Documents relating to the transfer 
can be found in the Office of the Administrative Director, NAIC. 

62. Drake and Sobel, pp. 180-185; Campbell 8 December 1993; Dedication publication, Cornell 
University, 1974, NHOB; National Science Board, Minutes of the Open Meetings, 168:2, National Science Board; 
NAIC QR Q3/1974, p. 10, Q2/1975, p. 4, and Q3/1975, p. 4. 



LITTLE SCIENCE/BIG SCIENCE 105 



As Don Campbell recalled: 'The initial feeds that we used with the transmitter need- 
ed cooling; we were having trouble attaching the cooling lines. People would line up late 
at night in front of the control room during this experiment. We would turn on the trans- 
mitter, and there would be this sort of flash of light, as things burned up up there and 
everybody went 'Ah!' It was a bit like fireworks. When the problem finally got solved, I 
think everyone was rather disappointed that there wasn't any flash of light up there!" 63 

The Arecibo S-band upgrade literally created a new instrument with which to do 
planetary radar astronomy, a field whose outer limits of capability still leaned strongly on 
the availability of new hardware. Although the Arecibo telescope made S-band radar 
observations of Mars beginning August 1975 for NASA's Viking mission, the arrangement 
with NASA freed Arecibo also to do radar research that was not mission related. So, late 
the following month, on 28 September 1975, the radar detected Callisto, followed two 
nights later by Ganymede, the first detections of Jupiter's Galilean moons. 64 

The NASA agreement guaranteed planetary radar astronomy an instrument and a 
research budget. Nowhere else did planetary radar astronomy operate with such extensive 
institutional and financial support. These unique advantages, combined with its relations 
with Cornell and MIT, have sustained Arecibo as the focal center of planetary radar 
astronomy to the present day. 



The JPL Mars Station 



In sharp contrast to Arecibo, JPL did not formally recognize planetary radar astron- 
omy as a scientific activity. Planetary radar had neither a budget line nor a program at JPL; 
it was invisible. Its role was to test the performance of the Deep Space Network (DSN) . Eb 
Rechtin, the architect of the DSN, deliberately avoided creating a radar astronomy pro- 
gram. He saw no reason, other than for science, why NASA ought to fund it. Instead, plan- 
etary radar became, in the words of JPL radar astronomer Richard Goldstein, the "cow- 
catcher on the DSN locomotive," financed at the "budgetary margin" of the DSN. In 
Goldstein's own words, "I was the cow-catcher and still am." 65 

Radio astronomy, on the other hand, held a more privileged position. Nick Renzetti, 
the DSN manager responsible for links between the Network and its users (NASA space 
missions), forged an agreement with NASA Headquarters that permitted qualified radio 
astronomers to perform experiments on Goldstone antennas at no cost, provided the 
experiments did not conflict with the antennas' prime mission, spacecraft communica- 
tions and data acquisition. 66 

Not only was JPL planetary radar astronomy invisible, but relations between JPL and 
its oversight institution, the California Institute of Technology, were about as distant as 
those between Lincoln Laboratory and MIT. JPL employees, like their peers at Lincoln 
Laboratory, could not have graduate students, unless they held a joint appointment at 
Caltech. Although Dick Goldstein taught a radar astronomy course at Caltech during the 
1960s, his students did not become radar astronomers, but went into other fields. An 
unusual case was Lawrence A. Soderblom, who took Goldstein's course in the fall of 1967. 
Soderblom later joined the U.S. Geological Survey, where he interpreted planetary radar 
data. 67 



63. Campbell 8 December 1993; Campbell 7 December 1993; NAIC QR Ql/1975, p. 4. 

64. NAIC QR Q3/ 1976, pp. 4-5. 

65. Goldstein 14 September 1993; Goldstein 7 April 1993; Rechtin, telephone conversation, 
13 September 1993. 

66. Renzetti 16 April 1992; Renzetti 17 April 1992. 

67. Soderblom 27 June 1994. 



1 06 TO SEE THE UNSEEN 



Unlike Lincoln Laboratory or Arecibo, JPL did not hire people to do radar astron- 
omy, because JPL officially did not have a radar astronomy program. Goldstein and Dewey 
Muhleman had participated in the 1961 Venus radar experiment, not because they were 
Caltech graduate students, but because they were JPL employees in Walt Victor's group. 
Roland Carpenter, another JPL planetary radar astronomer of the 1960s, also worked 
under Walt Victor. 68 Once Roland Carpenter and Dewey Muhlemen left JPL, Dick 
Goldstein remained the sole JPL radar astronomer for several years. 

Planetary radar astronomy subsisted at JPL during the 1960s on money earmarked 
for various space missions and on the budget of the DSN. The NASA budget then was 
more generous. NASA paid the cost of operating and maintaining the Goldstone radar as 
part of the DSN, so that the costs of the radar instrument were paid. When Goldstein 
needed a piece of hardware designed and built, he assigned the job to one of the employ- 
ees he supervised as manager of Section 331. The Advanced Systems Development bud- 
get of the DSN paid for hardware design and construction. 69 

In order to obtain time on the Goldstone radar, Goldstein went from mission to 
mission and explained why the mission ought to support his radar experiments. With 
approval from a mission, Goldstein could then request antenna time from the committee 
in charge of allocating antenna use. Mariner missions supported many of the radar obser- 
vations, while Viking and Voyager supported experiments on Mars, Saturn's rings, and the 
Galilean satellites of Jupiter. Officially, the experiments were done for neither radar 
improvement nor the science, but for "better communications" with spacecraft. 70 

If the NASA Headquarters Planetary Science Program, then headed by William 
Brunk, approved of a particular set of radar experiments, getting antenna time was much 
easier. As Goldstein explained, Brunk "would support me a little and I took that as a pos- 
itive thing, and I guess later on he turned that off, but it wasn't very big in the first 
place. ...It was a kind of a way to get legitimacy. If he funds you a little, that means it's 
important. If he doesn't fund you at all, that means it's not important....! would go to great 
lengths to get antenna time and a little funding from Brunk was helpful." 71 

Planetary radar astronomy at JPL thus came into existence and continued to func- 
tion because of the Laboratory's Big Science space missions and Deep Space Network 
activities. In particular, it was the idea, put forth by the DSN's chief architect Eb Rechtin, 
that radar astronomy would have the dual function of testing the DSN's ability to support 
interplanetary missions and developing new hardware for the DSN (that is, the justifica- 
tion for having Advanced Systems Development underwrite radar astronomy hardware). 
It was specifically for developing and testing new DSN hardware that, shortly after the 
1961 Venus radar experiment, Rechtin arranged with NASA to set aside a Goldstone radar 
for that purpose. On that instrument, Goldstein and Carpenter made Venus radar obser- 
vations during the 1962 and 1964 conjunctions. Planetary radar research benefitted from 
the developmental work, which increased the continuous-wave radar's average power out- 
put from 10 to 13 kilowatts in 1962 and then to 100 kilowatts for the 1964 Venus experi- 
ment. 72 

When Goldstein made observations during the 1967 Venus conjunction, however, he 
used a new, more powerful 64-meter-diameter (210-ft-diameter) S-band antenna, the Mars 
Station. The need to handle missions at ever increasing distances from Earth furnished 



68. Carpenter, telephone conversation, 14 September 1993. 

69. Jurgens 23 May 1994; Goldstein 14 September 1993; Downs 4 October 1994. 

70. Memorandum, Carl W. Johnson to Murray, 31 October 1977, 62/3/89-13, JPLA; Goldstein 
14 September 1993. 

71. Goldstein 14 September 1993. 

72. Victor, "General System Description," p. 3 in Goldstein, Stevens, and Victor, eds., Goldstone 
Observatory Report for October-December 1962, Technical Report 32-396 (Pasadena: JPL, 1 March 1965); Waff, 
ch. 6, pp. 17 & 19; Goldstein and Carpenter, "Rotation of Venus," pp. 910-911; Carpenter, "Study of Venus by CW 
Radar," p. 142. 



LITTLE SCIENCE/BIG SCIENCE 107 



the raison d'etre for JPL's entry into the Big Dish arena, and incidentally supplied its 
future radar astronomers with an ideal instrument for imaging and other planetary radar 
work. With the Mars Station, Goldstein and his colleagues discovered three rugged sec- 
tions of Venus; the largest received the name Beta. The needs of NASA space missions, not 
radar astronomy, dictated the design of the Mars Station. 

The Mars Station represented the DSN's commitment to the S-band and its need for 
large antennas capable of communicating with probes at great distances from Earth. 
Starting in 1964, all new space missions were to use the higher S-band. Despite the com- 
mitment to S-band, NASA still had active missions operating at lower frequencies. The 
switch to S-band throughout the Deep Space Network therefore required a hybrid tech- 
nology capable of handling missions operating at either the higher or lower frequency 
bands. A JPL design team devised the equipment, which was installed throughout the 
DSN. 

The hybrid equipment, however, was only a transitional phase before the construc- 
tion of more powerful and more sensitive antennas specifically intended to handle 
unmanned missions to the planets. In order to determine the essential characteristics and 
optimal size for those antennas, JPL initiated a series of studies in 1959 that culminated 
in the Advanced Antenna System. NASA's Office of Tracking and Data Acquisition, which 
oversaw the DSN, sponsored a pioneering conference on large antennas on 6 November 
1959. Speakers reported on three kinds of antennas: steerable parabolic dishes, fixed 
antennas with movable feeds (e.g., Arecibo), and arrays, the same antenna types consid- 
ered later by NSF panels. 

NASA and JPL decided to stay with the proven design of steerable dishes. The next 
decision was antenna size. JPL engineering studies showed that antenna diameters 
between 55 and 75 meters (165 and 225 ft) were near optimal and the most cost-effective. 
The final choice, 64 meters (210 ft), was the same size as the recently-completed 
Australian radio telescope at Parkes. This was no coincidence. JPL engineers had received 
a lot of help from the Australian designers. Their studies of the Parkes telescope provid- 
ed JPL engineers with a wealth of data and ideas to use in the design of their 64-meter 
(210-ft) dish. 

JPL also commissioned private firms to carry out feasibility and preliminary design 
studies for the Advanced Antenna System beginning in September 1960, before awarding 
a construction contract to the Rohr Corporation in June 1963. Construction proceeded 
after JPL analyzed and approved the Rohr design in January 1964. Rohr completed the 
antenna in May 1966, following the formal dedication on 29 April 1966. 



108 



TO SEE THE UNSEEN 




Figure 15 

JPL Goldstone Mars Station (DSS-14) upon completion in 1966. (Courtesy of Jet Propulsion Laboratory, photo no. 
333-5967BC.) 

The dish was dubbed the Mars Station, because its mission was to support Mariner 
on its journey to Mars in 1964, long before the antenna was operational. Nonetheless, on 
16 March 1966, the big dish received its first signals from Mariner 4 and provided opera- 
tional support for Pioneer 7, launched in August 1966. The Mars Station subsequently 
supported several other missions, including the first Surveyor flights, and made possible 
live Apollo television pictures from the Moon, not to mention planetary radar images and 
topographical maps. In order to systematize its growing number of antennas around the 
world, the DSN instituted a numbering system, so that each Deep Space Station (DSS) 
would bear a unique number. The original Echo antenna became DSS-12, while the anten- 
na used in the Venus radar experiments became DSS-13. The Mars Station was DSS-14. 73 

The Mars Station, as part of the Deep Space Network, underwent a major upgrade 
in the 1970s in order to accommodate the needs of the Viking and Mariner Jupiter-Saturn 
spacecraft (later known as Voyager) . For the Viking mission, each DSN station would have 
to handle six simultaneous data streams from the two Viking Orbiters and the one Lander. 



73. Corliss, Deep Space Network, pp. 37-38, 50, 60-61, 82, 84, 87, 129 and 131; Renzetti, A History, 
pp. 25-26, 32, 52 and 54; Robertson, pp. 255-261; The NASA/JPL 64-Meter-Diameter Antenna at Goldstone, 
California: Project Report, Technical Memorandum 33-671 (Pasadena: JPL, 15 July 1974), pp. 7-17; Rechtin, Bruce 
Rule, and Stevens, Large Ground Antennas, Technical Report 32-213 (Pasadena: JPL, 20 March 1962), pp. 7-10. 



LITTLE SCIENCE/BIG SCIENCE 109 



Viking, in fact, was a dual-frequency craft; it used both S-band and X-band frequencies. 
For the Mariner flight to Jupiter and Saturn, the telemetry rates were the same as those 
for Mariner 10, but the data were coded and transmitted at X-band from distances up to 
nine astronomical units. Operating in the higher X-band range gave the increased sensi- 
tivity needed to remain in contact with Mariner, as it flew by Jupiter and Saturn. 
Construction of the 400-kilowatt, X-band (8495 MHz; 3.5 cm) transmitter for the Mars 
Station was completed by Advanced Systems Development, and the DSS-14 began opera- 
ting at X-band in 1975. 74 

During the 1970s, the population of JPL planetary radar astronomers grew. Jurgens 
had an undergraduate and graduate degree in electrical engineering from Ohio 
University and had taught electrical engineering at Clarkson College (Ohio) , before pur- 
suing a doctoral degree at Cornell. Sometime after he finished researching his disserta- 
tion, a study of the radar scattering properties of Venus, at Arecibo, JPL hired Jurgens in 
1972 to serve on the technical staff of the Telecommunications Research Section, not to 
do planetary radar astronomy. 75 

Also working in Goldstein's section was George Downs, who had studied radio 
astronomy at Stanford University under Ronald Bracewell. Goldstein had Downs analyze 
Mars radar data and make observations at Goldstone to assist in the selection of the Viking 
landing site, a project funded by the Viking Project Office. The planetary radar work, how- 
ever, was in addition to his regular JPL duties, which involved studying newly discovered 
radio sources as potential timing sources for the Deep Space Network. 76 

During the heyday of the Viking Mars radar observations, Goldstein called upon 
other JPL employees, such as Howard C. Rumsey, Jr., who had a strong background in 
physics and mathematics, and the hardware experts George A. Morris and Richard R. 
Green. Jurgens described the atmosphere at JPL: "We all knew each other's talents. It was 
very efficient. Nobody ever felt like we were working terribly hard. It was just like a big 
playpen. Everybody came here, and we sort of did our thing and thought about what we 
wanted to do. We'd talk to each other, and we'd go out to lunch. It was the period of the 
long lunches sometimes. We had the Gourmet Society. The Gourmet Society was really 
headed by Howard Rumsey, who really liked good food. He would read the Sunday 
gourmet page and the Thursday gourmet page in the L. A. Times, and pick out interest- 
ing restaurants. At least one day a week, we went trudging off-lab to eat decent food at 
some interesting place that Howard had selected. These things often involved bicycle trips 
as far as Long Beach." 77 

Once Viking project funding ended in 1976, JPL radar astronomy hit hard times. 
Getting time on the DSN become more difficult. It was easy to get time in the early and 
middle 1960s, when the DSN was tracking few spacecraft. As Dick Goldstein explained: 
"Back in the sixties I thought of myself as director of the Goldstone Observatory. I got to 
choose what we could do, if I could get support for it." 78 During the 1960s, the JPL radar 
experiments conducted on Venus involved hundreds of hours of runs; for example, the 
1961 Venus experiment involved 238 hours of data collected over two months. But by the 
end of the decade, the amount of time available had declined. The JPL 1969 Venus obser- 
vations were not made daily for a period of months during inferior conjunctions, but only 
"on 17 days spaced from 11 March to 16 May 1969." 79 



74. Rob Hartop and Dan A. Bathker, The High-Power X-Band Planetary Radar at Goldstone: Design, 
Development, and Early Results," IEEE Transactions on Microwave Theory and Techniques MIT-24 (December 1976): 
958-963; JPL Annual Report, 1974-1975, p. 22.JPLA. 

75. Jurgens 23 May 1994. 

76. Downs 4 October 1994. 

77. Jurgens 23 May 1994. 

78. Goldstein 14 September 1993. 

79. Golomb, "Introduction," in Victor, Stevens, and Golomb, p. 4; Goldstein and Howard C. Rumsey, Jr., 
"A Radar Snapshot of Venus," Science 169 (1969): 975. 



110 TO SEE THE UNSEEN 



The reduction in available antenna time was in direct proportion to the increasing 
number of spacecraft with which the Deep Space Network communicated. By 1977, the 
DSN was in communication with a record 14 spacecraft. In addition to the three Viking 
craft (two orbiters and one lander), the DSN communicated with Helios 1 and 2, Pioneer 
11 (Saturn), Pioneer 10 (which was leaving the solar system), Voyagers 1 and 2, and 
Pioneers 6, 7, 8, and 9. That number grew to 19, a new record, the following year, when 
the DSN also handled communications with Pioneer Venus, which was an orbiter and four 
probes. 80 

Then the Deep Space Network stopped funding radar astronomy hardware. The abil- 
ity to carry out radar astronomy without official recognition was maintained thanks to the 
presence at high levels of JPL management of Eb Rechtin and Walt Victor, who watched 
over planetary radar activities. But Rechtin left JPL, and Victor transferred in December 
1978 from the DSN to the Office of Planning and Review. 81 Without their guardianship, 
JPL radar astronomy was vulnerable. 

As Goldstein explained: "From a chauvinistic point of view, it was a disaster, because 
the rest of the world passed us by.. ..We went from being a couple years ahead to being a 
couple years behind." 82 Without funding for hardware, the radar system was at risk. 
Moreover, the Goldstone Mars Station was in desperate need of repairs, and the equip- 
ment was becoming harder and harder to maintain. In 1976, the antenna already was ten 
years old, and the electronic equipment transferred to the Mars Station from the Venus 
Station (DSS-13) was even older. 83 

The termination of Deep Space Network funding of planetary radar astronomy grew 
out of two concerns, one within JPL and the other within the Deep Space Network. One 
of Bruce Murray's chief concerns after taking over as laboratory director was the state and 
status of science and scientists at JPL. The basic criticism was that JPL lacked a commit- 
ment to scientists. But the problem had a cultural side; technologically-centered team- 
work dominated laboratory culture. Also, many of those doing science were like Dick 
Goldstein and Ray Jurgens; trained and hired as electrical engineers, they carried out 
radar astronomy science experiments. Murray made the problem the topic of mini- 
retreats, meetings, and seminars and, as a first step in elevating the status of science at JPL, 
appointed in October 1977 the first JPL chief scientist, Caltech physics professor Rochus 
E. Vogt, who had authored a report on relations between Caltech and JPL, another topic 
of great concern. 84 

Despite, or rather because of, Murray's concerns for science at JPL, planetary radar 
astronomy did not fair well under his reign as laboratory director. Goldstein was trans- 
ferred out of the section where he had guided and supported the JPL planetary radar 
effort. JPL management decided that it was not proper to do science under the guise of 
improving the DSN. Radar astronomy should compete with other JPL science activities, 
and the Office of Space Science and Applications (OSSA; now the OSSI, Office of Space 
Science and Instruments) at NASA Headquarters should fund it, they ruled. 85 

At the same time, the DSN budget was suffering from monetary and manpower lim- 
itations. 86 To make matters worse, a routine review of the Deep Space Network, chaired 



80. JPL Annual Report, 1976-1977, p. 22, and ibid., 1978, p. 20, JPLA. 

81. Murray to Allen M. Lovelace, 30 November 1978, 75/5/89-13, JPLA. 

82. Goldstein 14 September 1993. 

83. Jurgens 23 May 1994. 

84. Agenda, Director's Mini-Retreat, "How Does Science Fit In at JPL?," 22 March 1977, 55/3/89-13; 
Director's Letter, no. 22, 30 September 1977, 61/3/89-13; Roger Noll to Murray, 23 November 1977, 63/3/89- 
13; and typed manuscript, First Annual "State of the Lab" Talk by Murray to Management Personnel, 1 April 
1977, 55/3/89-1 3, JPLA. 

85. Goldstein 14 September 1993. 

86. Notes from a discussion of TDA problems discussed during a mini-retreat held 8 November 1977, 
63/3/89-13, JPLA; Jurgens 23 May 1994; and Stevens 14 September 1993. 



LITTLE SCIENCE/BIG SCIENCE 1 1 1 



by Eb Rechtin, declared that radar astronomy was no longer the "cow-catcher" of the DSN, 
meaning that the role of radar astronomy in creating new hardware to help drive forward 
the Deep Space Network had come to an end. It was, therefore, time to pull the plug on 
planetary radar astronomy, after previous reviews had lauded it. 

From time to time, acting under instruction from NASA Headquarters, the Deep 
Space Network called into existence the TDA (Tracking and Data Acquisition) Advisory 
Panel to review DSN long-term plans. Planetary radar was held high as an integral part of 
DSN development activities by Ed Posner, a DSN manager. Among the hardware contri- 
butions of radar astronomy he listed were microwave components, signal processing tech- 
niques, and station control concepts, all of which were tested in a "realistic environment." 
Planetary radar fell from that favorable position during the 1978 review. The head of the 
review panel, now called the DSN Advisory Group, was none other than Eb Rechtin, the 
architect of the Deep Space Network and the one responsible for making planetary radar 
a testbed of DSN technology. DSN management asked the panel to consider, among many 
other questions, radar astronomy. In the opinion of the Advisory Group, which Eb 
Rechtin wrote, "Another DSN technology which may have had its day as a foundation for 
DSN technology is DSN radar astronomy. Radar astronomy served the DSN very well for 
many years. The Advisory Group wonders what the next area might be." 87 Radar astrono- 
my no longer produced the cutting edge hardware that justified the support of Advanced 
Systems Development. As a result, planetary radar astronomy at Goldstone went begging 
for money. 

A good part of the problem was the perception of planetary radar as just a testbed 
for DSN technology. The value of the science was simply not recognized by either DSN 
management or NASA Headquarters. After all, in accordance with Eb Rechtin's plan, 
planetary radar was not to occupy a budget line nor to have program status; it was simply 
a DSN activity to assist in the development and testing of new technology. 

The lack of money to even maintain the Goldstone radar, whose age and one-of-a- 
kind design engineering made it all that much harder to maintain, began to frustrate the 
performance of experiments. By 1980, the Goldstone radar was in such bad shape that 
planetary radar astronomy experiments were no longer carried out on a regular basis. The 
radar was resurrected for attempts at asteroid 4 Vesta on 28 May 1982 and comets IRAS- 
Araki-Alcock and Sugano-Saigusa-Fujikawa in 1983, but only Comet IRAS-Araki-Alcock was 
detected successfully. As Ray Jurgens reflected on the situation: "Basically, it looked like it 
was the end of the radar." 88 

Goldstack 

In discussing radar systems available for planetary research, an instrument that one 
must not overlook is the bistatic Goldstack radar, which used Haystack as the transmitting 
antenna and the JPL Goldstone DSS-14 radar as the receiving antenna. In the past, plan- 
etary radar astronomers seldom used bistatic radars, let alone radars requiring the 
coordination of two unrelated institutions. Bistatic radars require a daunting amount of 
coordination on both the technical and institutional level. Nonetheless, transmitting 
power and antenna receiver sensitivity can combine to create a radar capable of doing 
more than either facility operating monostatically. In theory, Goldstack could outperform 
either Haystack or DSS-14 separately and achieve a nearly tenfold increase in overall radar 
performance. 



87. TDA Advisory Panel, 1971-1972," and TDA Advisory Council, 1978-1981," JPLPLC. 

88. Jurgens 23 May 1994; Jurgens, "Comet Iras," pp. 222 and 224. 



112 TO SEE THE UNSEEN 



When radar astronomers Irwin Shapiro and Gordon Pettengill pitched Goldstack to 
NASA in 1968, they outlined an ambitious program of research: 1) observations of the 
Galilean satellites Ganymede and Callisto; 2) maps of the surfaces of Mercury and Venus; 
3) a Moon-Earth-Moon triple-bounce experiment to study the Earth's radar-reflecting 
properties; 4) topographical studies of Mars at a resolution of 150 meters; and 5) a radar 
test of General Relativity. 89 Haystack and JPL engineers worked out the technical details 
of those experiments, and by May 1970 JPL had installed an X-band maser tunable to the 
Haystack frequency. The demands of the space program on the Mars Station, however, 
forced postponement of the experiments. As Shapiro recalled: "DSN always had schedul- 
ing problems. Scheduling was the biggest pain in the neck. From the point of view of sci- 
ence, I never felt the best things were done with scheduling; the engineering and mission 
pressures were too enormous. It always seemed to be as impossible as possible to schedule 
ground-based science experiments, but good science, in fact, was done." Goldstack even- 
tually searched for Ganymede and Callisto in late May and early June 1970. 90 



Jodrell Bank 



Several years before planetary radar astronomy ended at Haystack and declined at 
JPL, radar research at Jodrell Bank came to an end, too. In contrast to JPL, Jodrell Bank 
officially recognized and funded its radar astronomy program, and Sir Bernard Lovell 
proudly and, in the face of adversity, stubbornly maintained radar research. The Jodrell 
Bank facility was an example of British Big Science; private and civilian governmental 
funding underwrote the building of the large dish. While the U.S. military funded some 
meteor radar research, Jodrell Bank radar astronomy was not, in any sense, an extension 
of American Big Science. The demise of planetary radar astronomy at Jodrell Bank was a 
lesson in the dangers inherent in Little Science, not Big Science. 

Thanks to NASA and the American military, Jodrell Bank did not lack for radar 
equipment. The still secret agreement between Lovell and an unidentified Air Force offi- 
cer had as its immediate objective the sending of commands to the Pioneer 5 spacecraft. 
The U.S. Air Force funded Space Technology Laboratories (STL), a Los Angeles-based 
wholly-owned subsidiary of Ramo-Wooldrige (later TRW), to install a continuous-wave 
410.25-MHz (73-cm) radar transmitter and other equipment on the Jodrell Bank tele- 
scope in order to track lunar rocket launches. Although the STL transmitter had only a 
few kilowatts of power, it was stable, reliable, and free of the problems that plagued the 
pulse radar apparatus pieced together by John Evans. Ownership of the STL transmitter 
passed to NASA, which provided operational funds between 1959 and 1964 to track rock- 
et launches, not to perform radar experiments. NASA left the equipment on the Jodrell 
Bank antenna "on an indefinite loan basis," so that the University of Manchester might 
use it for scientific research. 91 



89. Memorandum, NEROC Project Office to Wiesner, 19 September 1968, regarding "Proposed 
Contact with Newell Regarding Possible Partial Support of Haystack by NASA," 8/2/AC 135, MITA; NEROC, 
Proposal to the National Science Foundation for Programs in Radio and Radar Astronomy at the Haystack 
Observatory, 8 May 1970, pp. III.8-III.10, 1 .1.1 A; Brunk to Distribution List, 4 October 1968, NHOB. 

90. Shapiro 4 May 1994; Shapiro 1 October 1993; "Funding Proposal, 'Plan for NEROC Operation of 
the Haystack Research Facility as a National Radio/Radar Observatory,' NSF, 7/1/71-6/30/73," 26/2/AC 135, 
and Sebring to Hurlburt, 27 March 1970, 1 8/2/AC 135, MITA; NEROC, Proposal to the National Science 
Foundation for Programs in Radio and Radar Astronomy at the Haystack Observatory, 8 May 1970, pp. Ill .8- 
III. 10, LLLA; JPL 1970 Annual Report, p. 14, JPLA. 

91. Lovell, 11 January 1994; Evans 9 September 1993; Ponsonby 11 January 1994; Lovell, "Astronomer 
by Chance," pp. 322-325 and 328-329; Edmond Buckley to R. G. Lascelles, 8 November 1961, and related doc- 
uments in 2/53, Accounts; Able, Thor, and Pioneer 5 materials in 4/16, Jodrell Bank Miscellaneous; materials 
in 1/4, Correspondence Series 2; 2/53, 2/52, 2/55, 7/55, 8/55, 1/59, and 3/59, Accounts; and 4/16, Jodrell 
Bank Miscellaneous, JBA. 



LITTLE SCIENCE/BIG SCIENCE 1 1 3 



In 1962, the Jodrell Bank radar group consisted of only John Thomson and his grad- 
uate student John E. B. Ponsonby. Evans had sought his fortune at Lincoln Laboratory. As 
Ponsonby characterized the radar group, "We were always two men and a boy [K. S. 
Imrie]." When Ponsonby arrived at Jodrell Bank in 1960, he was shocked to discover that 
he was the only one in the radar group with a flare for electronics; Thomson, according 
to Ponsonby, was happy doing computations. Jodrell Bank radar astronomy was small not 
only in terms of staff, but also in observing time, which varied between 1 and 10 percent. 92 

Thomson and Ponsonby abandoned much of the equipment Evans had been using; 
they used a simpler approach with less technical risk. The old apparatus used vacuum 
tubes; the new was all solid-state digital electronics. A grant from the DSIR underwrote the 
cost of these modifications, as well as the purchase of a parametric amplifier and spare kly- 
stron tubes. The 1962 and 1964 Jodrell Bank Venus radar experiments were carried out 
with this digital continuous-wave equipment. 93 

The focus of Jodrell Bank's Venus radar research after 1962 was a bistatic experiment 
with the Soviet Long-Distance Space Communication Center located near Yevpatoriya in 
the Crimea. The experiment was possible only because Lovell had succeeded in thawing 
Cold War relations. The opportunity came in March 1961, when Soviet space trackers lost 
contact with a Venus probe launched the previous month. The Soviet Academy of Sciences 
approached Lovell to use the Jodrell Bank telescope to search for signals. As the months 
passed, and Jodrell Bank attempted to make contact with the probe, communications 
between the British and Soviets increased. The collaboration led to the establishment of 
a telex link between Jodrell Bank and the Yevpatoriya radar station, as well as an invitation 
for Lovell to visit the Soviet Union two years later. 

The idea of doing the bistatic experiment came to Lovell during his visit to 
Yevpatoriya, when he discovered the extremely powerful Soviet transmitter. Vladimir 
Kotelnikov, who headed the Soviet planetary radar effort, joined Lovell as the other mov- 
ing spirit behind the bistatic project. An Iron Curtain of secrecy hindered the project, 
however. In order to set up the bistatic radar, Jodrell Bank had to know the frequency and 
precise coordinates of the Yevpatoriya radar. The Soviets were loathe to disclose their fre- 
quency, transmitter size, location, or even antenna dimensions, but the British established 
those parameters step by step. Nonetheless, the experiment did not work initially, because 
Jodrell Bank lacked the correct Doppler shift. After testing the bistatic arrangement on 
the Moon, the Yevpatoriya facility began to transmit radar signals to Venus, and Jodrell 
Bank received them from January through March 1966. Data tapes were delivered to 
Kotelnikov by way of the British Embassy. As a long-distance bistatic radar experiment, the 
effort was a first. However, it was an opportunity lost. 94 

Ponsonby set forth a cogent analysis of the bistatic Venus experiment in his disserta- 
tion: "Planetary radar has proved to be a field in which new results are only obtained by 
the groups which have the most sensitive systems and the data processing capacity to make 
the best use of the data acquired. In both respects the group at Jodrell Bank has never 
been in a leading position." 95 

Lovell disagreed; the bistatic experiment was 'just too late." JPL and Lincoln 
Laboratory already had determined the rate and direction of rotation of Venus. "But if 



92. Ponsonby 1 1 January 1994; summaries of telescope use in 1/2, Correspondence Series, JBA. 

93. Ponsonby 11 January 1994; 2/51, Accounts, JBA; Ponsonby, Thomson, and Imrie, "Radar 
Observations of Venus," pp. 1-17; Ponsonby, Thomson, and Imrie, "Rotation Rate of Venus Measured by Radar 
Observations, 1964," Nature 204 (1964): 63-64. 

94. Lovell, 1 1 January 1994; Ponsonby 1 1 January 1994; Lovell, "Astronomer by Chance," pp. 370-372; 
Lovell, Out of the. Zenith, pp. 186-188 and 201-204; Ponsonby and Thomson, "U.S.S.R.-U.K. Planetary Radar 
Experiment," pp. 661-671 in R. W. Beatty, J. Herbstreit, G. M. Brown, and F. Horner, eds., Progress in Radio Science, 
1963-1966 (Berkeley: URSI, 1967); Ponsonby, "Planetary Radar," pp. 6.11-6.22. 

95. Ponsonby, "Planetary Radar," p. 6.21. 



114 TO SEE THE UNSEEN 



only my 1963 conversations and agreement with the Soviet Union could have been facili- 
tated without trouble at this end and without trouble at the transmitter," Lovell argued, 
"we would have been first on that." 96 

Lovell's analysis, as well as that of Ponsonby, raises the vital question of the ability of 
the Jodrell Bank radar group to effectively compete against American radar astronomers. 
The STL transmitter operated in the UHF band (410.25 MHz; 73 cm). Although the 
Arecibo Observatory operated in the same band, the trend in planetary radar astronomy 
was toward higher frequency ranges, the S-band at JPL (and later at Arecibo) and the X- 
band at Haystack. The higher frequencies allowed the radar to do much more radar 
astronomy science than was possible at UHF. 

Ponsonby raised another point in his dissertation: "If a true state-of-the-art transmit- 
ter were acquired it would cost an appreciable fraction of the cost of the telescope, and 
clearly to justify investment on that scale it would have to be used much more extensively 
than would be compatible with the predominantly passive radio astronomical programs at 
Jodrell Bank. Passive radio-astronomy may appropriately be done as a secondary line of 
research at a primarily radar installation, but experience has shown that the two activities 
do not combine well the other way. Appreciating this, the research reported in this thesis 
is not, at least for the present, being pursued further." Indeed, Ponsonby continued, 'The 
limited computing facilities available in the University and the lack at the time of on-line 
computers at Jodrell Bank in effect prevented a thorough analysis of the data that was 
acquired, and this took away much of the value of the observations." 97 

The acquisition of new radar and computer equipment certainly would have consti- 
tuted a significant expenditure, but Lovell probably could have raised the necessary 
money. Could Jodrell Bank have kept up with the development of planetary range- 
Doppler mapping in the United States? Thomson was working on an aperture synthesis 
technique for making lunar radar maps. The mathematical process for constructing the 
image was analogous to that now used for tomographic brain scanners and differed entire- 
ly from that used in the United States to construct range-Doppler maps. The technique 
was not very practical, however; it required computer capacity not then available at Jodrell 
Bank and ultimately could not be generalized to the planets. 98 

In the end, the small scale of planetary radar astronomy at Jodrell Bank did it in. 
Thomson and Ponsonby grew tired of the Soviet bistatic Venus experiment. They carried 
the main load of the work at irregular hours of the day and night. Finally, on 18 March 
1966, Thomson and Ponsonby could take no more. They handed Lovell a list often good 
reasons for ending the experiment. Kotelnikov agreed to "an interval" in the observations, 
which never resumed. 99 Ponsonby remained rather cynical about the venture, which he 
has characterized as a political exercise. 'The signals were recorded on magnetic tape and 
sent off to Russia, and I never heard from them again!" 100 

Ponsonby already was tired of the bistatic experiments, when the death of John 
Thomson from an inoperable brain tumor in August 1969 devastated the Jodrell Bank 
planetary radar program. Without Thomson, and certainly without Ponsonby's interest, 
Jodrell Bank had no radar group. Through sheer stubbornness, however, Lovell tried to 
keep the radar program going. In October 1969, he and his Jodrell Bank colleagues drew 
up a scientific program for a proposed 122-meter (400-ft) telescope, the Mark V. The pro- 
gram included a series of planetary radar experiments outlined by Ponsonby. Was this the 



96. Lovell 11 January 1994. 

97. Ponsonby, "Planetary Radar," pp. 6.21-6.22. 

98. Ponsonby 11 January 1994; Lovell, "Astronomer by Chance," pp. 373-375; various documents in 
2/51, Accounts, JBA. 

99. Lovell, Out of the Zenith, pp. 207-208. 

100. Ponsonby 1 1 January 1994. 



LITTLE SCIENCE/BIG SCIENCE 1 1 5 



telescope that could have revived Jodrell Bank radar research? Like its American cousin 
the NEROC telescope, the Mark V was never built. In retrospect, Lovell realized that "It 
was now out of the question for us to continue....! saw the passing of radar as inevitable, 
but with regret." 101 

The sixties was the era of the Big Dish; large antenna projects came and went, and 
so did planetary radars. In 1965, four antennas supported planetary radar experiments: 
Arecibo, Haystack, Jodrell Bank, and the Goldstone Mars Station. A fifth dish, the NEROC 
telescope, was on the drawing board. But ten years later, the NEROC telescope had not 
been built; Haystack and Jodrell Bank no longer performed planetary radar experiments. 
By 1980, Goldstone had joined their number. Only Arecibo remained. Planetary radar 
astronomy appeared to be a collapsing field. 

At Arecibo, nonetheless, radar astronomy had found a patron in NASA. Planetary 
radar there also had a recognized and guaranteed budget, as well as a world-class research 
instrument, and both Cornell and MIT fed graduate students to the Arecibo facility. Given 
the financial, institutional, technological, and other resources available at Arecibo for 
planetary radar astronomy, one would have expected the field to have occupied an 
increasing amount of antenna time from 1974, when Haystack ceased radar astronomy, to 
1980, when JPL activity virtually ended. Instead, antenna use remained relatively stable, 
averaging about six percent between 1971 and 1980 and passing seven percent concur- 
rently with the inferior conjunctions of Venus. 102 

In terms of personnel, one could count the field of planetary radar astronomy as 
consisting of nine individuals. At MIT was Gordon Pettengill; at JPL, Dick Goldstein, Ray 
Jurgens, and George Downs. The Arecibo Observatory supported four radar practition- 
ers: Don Campbell, associate director at the Arecibo Observatory since 1979; John 
Harmon, AO research associate since 1978; Steven J. Ostro, Cornell assistant professor of 
astronomy since 1979; and Barbara Ann Burns, a graduate student of Don Campbell. 

In 1980, planetary radar astronomy was indeed a small field in terms of available 
instrumentation and active practitioners. It was an example of Little Science, but one 
which depended on Big Science for its very existence. Moreover, although that Big 
Science had been as diverse as military, space, ionospheric, and radio astronomy research 
at the emergence of radar astronomy, by 1980 Big Science had come to mean one thing: 
NASA. The financial and institutional arrangements with NASA influenced the kind of sci- 
ence done. In order to understand how that science was influenced, we must first look at 
the evolution of planetary radar astronomy as a science. 



101. Lovell 1 1 January 1994; Ponsonby 1 1 January 1994; Lovell, Out of the Zenith, p. 203; Lovell, TheJodreU 
Bank Telescope, Chapters 5-6 and 9-10, especially pp. 55-56 and 257. In analyzing the demise of radar astronomy 
at Jodrell Bank, though the smallness of the active radar astronomy staff, technical and technological factors, 
and the American lead had a more determinant role, to be sure, one must not overlook the lure of radio astron- 
omy. 

102. These figures are based on the NAIC quarterly reports for the years 1971-1980. The percentage of 
radar use annually was 2.9 percent in 1971; 9.5 percent in 1972; 6.9 percent in 1973; 1.9 percent in 1974; 7.2 per- 
cent in 1975; 5.8 percent in 1976; 7.3 percent in 1977; 4.7 percent in 1978; 5.0 percent in 1979; and 7.8 percent 
in 1980. The average percentage for the period 1971-1980 was 5.9, while the average for 1971-1975 was 5.68 per- 
cent and for 1976-1980 6.12 percent 



Chapter Five 

Normal Science 



Starting with the initial detections of Venus in 1961, planetary radar astronomy grew 
rapidly by discovering the rate and direction of Venus's rotation, by refining the value of 
the astronomical unit, and by rectifying the rotational period of Mercury. Data gathered 
from radar observations made at Haystack, Arecibo, and Goldstone formed the basis for 
precise planetary ephemerides at JPL and Lincoln Laboratory. In sum, the results of plan- 
etary radar astronomers served the needs of the planetary astronomy community. In addi- 
tion, radar also served to test Albert Einstein's General Theory of Relativity. 

Planetary radar astronomy concerned itself with two different but related sets of 
problems. One set of problems related to planetary dynamics and ephemerides, for 
instance, orbits, rotational and spin rates, and the astronomical unit. A second set related 
to the radar characteristics, or what is called the radar signature, of the planets, such as 
surface scattering mechanisms, dielectric constants, and radar albedos. The latter prob- 
lems are epistemological; that is, they deal with how radar astronomers know what they 
know. 

What defines this second set of epistemological problems is the fact that planetary 
radar astronomy is based on the use of techniques particular to radar. These problems 
have remained unchanged over time. In contrast, the first set of problems, those dealing 
with planetary and dynamics ephemerides, have changed over time. The nature of that 
change has been additive; at each stage of change, new problems are added to the old 
problems, which remain part of the set of problems radar astronomers seek to solve. 

Both the epistemological and scientific sets of problems are interrelated. For exam- 
ple, planetary radar astronomers derive the ability to solve astronomical problems out of 
the resolution of epistemological questions. The development of range-Doppler mapping, 
for example, led to the solution of a set of problems entirely different from ephemerides 
problems, yet the solution of ephemerides problems was sine qua non to the creation of 
range-Doppler maps. Conversely, the attempts to solve certain scientific questions 
required reconsideration of the radar techniques themselves. 

The philosopher of science Thomas S. Kuhn has attempted to explain the conduct 
of scientific activity. 1 Although Kuhn has used the term "paradigm" differently over time, 
initially it had a limited meaning. Stated simply, a paradigm, as used by Kuhn, is a core of 
consensus within a group of practitioners. The essence of the paradigm consensus is a set 
of problems and their solutions. Planetary radar astronomy quickly achieved and main- 
tained a paradigmatic consensus on which problems to solve. 

Moreover, the field often achieved scientific success by solving problems left 
unsolved or unsatisfactorily solved by optical means. Just as radar astronomy had resolved 
earlier that meteors were part of the solar system, so the determination of the rotational 
rates of Venus and Mercury and the refinement of the astronomical unit were astronomi- 
cal problems inadequately solved by optical methods, but resolved through the analysis of 
radar data. 



1. The works of Kuhn, which span over thirty years, have been summarized, explained, and analyzed 
in Paul Hoyningen-Huene, Reconstructing Scientific Revolutions: Thomas S. Kuhn's Philosophy of Science, trans. 
Alexander T. Levine (Chicago: University of Chicago Press, 1993). Especially relevant to the discussion here are 
pp. 134-135, 143-154, 169, 188-190 and 193-194. 

117 



118 TO SEE THE UNSEEN 



For Kuhn, "normal science" was a specific phase of scientific development distin- 
guished by universal consensus within a given scientific community over the problems to 
be solved and the ways of solving those problems. In other words, normal science was 
paradigm science. Preceding its evolution into normal science, according to Kuhn, a 
scientific activity passes through a developmental phase in which the problem-solving 
consensus that characterizes normal science does not yet exist. In this "preconsensus" or 
"pre-paradigm" phase, and immediately before a phase of normal science, groups of inves- 
tigators addressing roughly the same problems but from different, mutually incompatible 
standpoints compete with each other. As a consensus emerges, members of the compet- 
ing schools join the group whose achievements are better, as measured by scientific values. 

Planetary radar astronomy did not pass through Kuhn's "preconsensus" phase, how- 
ever. Complementary, not competing, groups marked the emergence of the field. The 
"bistatic radar" approach of Von Eshleman at Stanford University complemented the 
efforts of ground-based planetary radar astronomers, and that complementarity had been 
Eshleman's intention. 2 Ground-based planetary radar astronomers distinguished them- 
selves from the Stanford approach. In a review article on planetary radar astronomy 
published in 1973, Tor Hagfors and Donald B. Campbell, both at the Arecibo 
Observatory, explained, "We have, however, chosen to omit this work [space-based radar] 
here since it is our opinion that it properly belongs to the realm of space exploration 
rather than to astronomy." 3 Space exploration versus astronomy, then, was how planetary 
radar astronomers established turf lines. 

Planetary radar astronomy was, above all else, a set of techniques used with large- 
scale ground-based radar systems. As a result, planetary radar was an algorithm in search 
of a problem, a data set in search of a question. Hence, the success of planetary radar inex- 
orably depended on its ability to link its techniques and results to the problem-solving of 
a scientific discipline. Initially, those problems came from planetary astronomy, but as the 
types of techniques accumulated, radar came to solve new problems posed by planetary 
geology. Furthermore, the solving of those problems tied planetary radar astronomy to 
NASA's space missions. 

Despite its mercurial nature, planetary radar astronomy did exhibit an essential char- 
acteristic of Kuhn's normal science, a paradigm. The paradigm consisted of a consensus on 
a particular set of problems (e.g., orbital parameters) and agreement on a particular way 
of solving those problems (the analysis of range, Doppler, and other radar data obtained 
with ground-based radars from solar system objects) . The detections of Venus, Mercury, 
and Mars between 1961 and 1963 opened the field, but rotational rates, as well as the 
refinement of the astronomical unit, established the field. With the successful application 
of range-Doppler mapping to Venus, the paradigm began to shift in a new direction. 

Around the Sun in 88 Days 

The first radar detection of Mercury was announced by the Soviet scientists working 
under Vladimir A. Kotelnikov and associated with the Institute of Radio Engineering and 
Electronics (IREE) of the Soviet Academy of Sciences and the Long-Distance Space 
Communication Center near Yevpatoriya, in the Crimea. Kotelnikov's group made 53 
radar observations of Mercury during the inferior conjunction with that planet in June 
1962. At that time, the distance from Earth to Mercury was between 83 and 88 million 



2. Eshleman 9 May 1994. 

3. Hagfors and Campbell, "Mapping of Planetary Surfaces by Radar," Proceeding! of the IEEE 61 
(September 1973): 1219-1225, esp. 1224. 



NORMAL SCIENCE 119 



kilometers, twice the distance to Venus during inferior conjunction. Although the weak- 
ness of the return echoes prevented their use as a reliable indicator of the astronomical 
unit, Kotelnikov and his colleagues claimed a technical tour de force and a first in plane- 
tary radar astronomy. 4 

Richard Goldstein and Roland Carpenter at JPL took up the Soviet challenge and 
bounced radar waves off Mercury the following year in May 1963 using the Goldstone 
experimental radar. The experiment established a distance record that overshadowed the 
Soviet claim. Mercury was then farther from Earth, over 97 million kilometers away. In 
addition, the JPL experiment confirmed what astronomers already knew about Mercury, 
that its period of rotation was 88 days. Goldstein had no reason to believe it was other- 
wise. 5 

However, when Gordon Pettengill and Rolf Dyce observed Mercury in April 1965 
with the new Arecibo telescope, they reported a rotational rate of 59 5 days. This dis- 
covery, one of the earliest major achievements of planetary radar astronomy, astounded 
astronomers, who sought to explain the new, correct rotational rate. As Pettengill and 
Dyce concluded, 'The finding of a value for the rotational period of Mercury which dif- 
fers from the orbital period is unexpected and has interesting theoretical implications. It 
indicates either that the planet has not been in its present orbit for the full period of geo- 
logical time or that the tidal forces acting to slow the initial rotation have not been cor- 
rectly treated previously." 6 

Pettengill, Dyce, and Irwin Shapiro next published a lengthier discussion of their 
radar determination of Mercury's 59-day rotational period based on additional observa- 
tions made in August 1965. 7 Working with Giuseppe "Bepi" Colombo, an astronomer 
from the University of Padova visiting the Smithsonian Astrophysical Observatory, Shapiro 
began to develop an explanation for the new rotational period. Colombo, Shapiro 
recalled, "realized almost immediately that 58.65 days was exactly two-thirds of 88 days. 
Mercury probably was locked into a spin such that it went around on its axis one-and-a- 
half times for every once around the planet. The same face did not always face the Sun. 
That meant that near Mercury's perihelion, that is, when its orbit is closest to the Sun, 
Mercury tends to follow the Sun around in its orbit. Near perihelion, then, the orbital 
motion and spin rotation of Mercury were very closely balanced, so that Mercury almost 
presented the same face to the Sun during this period." 8 

In a joint paper, Colombo and Shapiro analyzed Mercury radar data, as well as opti- 
cal observations from the past, and presented a preliminary model. 9 In a seminal paper, 
Peter Goldreich and Stanton J. Peale pointed out the need to consider the capture of 
Mercury into the resonant rotation as a probabilistic event. If initial conditions during the 



4. Kotelnikov, G. Ya. Guskov, Dubrovin, Dubinskii, Kislik, Korenberg, Minashin, Morozov, Nikitskiy, 
Pctrov, G. A. Podoprigora, Rzhiga, A. V. Frantsesson, and Shakhovskoy, "Radar Observations of the Planet 
Mercury," Soviet Physics Doklady 1 (1963): 1070-1072. Given the stated weakness of the Mercury echoes, as well 
as their difficulty in obtaining accurate and verifiable Venus results, the Soviet announcement of a detection of 
Mercury, a much farther radar target than Venus, raised doubts in the United States about the validity of the 
Soviet claims. 

5. Carpenter and Goldstein, "Radar Observations of Mercury," Science 142 (1963): 381. 

6. Pettengill and Dyce, "A Radar Determination of the Rotation of the Planet Mercury," Nature 206 
(19 June 1965): 1240. 

7. Dyce, Pettengill, and Shapiro, "Radar Determination of the Rotations of Venus and Mercury," The 
Astronomical Journal 72 (1967): 351-359. 

8. Shapiro 30 September 1993; Giuseppe Colombo, "Rotational Period of the Planet Mercury," Nature 
208 (1965): 575. 

9. Colombo and Shapiro, "The Rotation of the Planet Mercury," The Astrophysical Journal 145 (1966): 
296-307. Earlier, it had appeared as an internal SAO publication: Colombo and Shapiro, The Rotation of the Planet 
Mercury, SAO special report no. 188 (Cambridge: SAO, 13 October 1965). 



120 TO SEE THE UNSEEN 



formation of the solar system had been slightly different, the capture may not have taken 
place. 10 

Irwin Shapiro's graduate student, Charles C. Counselman III, then did his doctoral 
thesis on the rotation of Mercury. Counselman developed a theory of capture, escape, 
recapture, and escape, as the eccentricity of Mercury's orbit changed, in a two-dimen- 
sional statistical model of the capture problem. Later, Norman Brenner, a graduate stu- 
dent working with both Shapiro and Counselman, expanded the analysis into a three- 
dimensional model in his 1975 doctoral dissertation. Meanwhile, Stan ton Peale published 
his own three-dimensional analysis. 11 

The Outer Limits 

Although Venus became the prime target of planetary radar astronomers, other 
planets drew their attention from the earliest opportunity to detect echoes from that plan- 
et. Richard Goldstein made the first radar detection of Mars during the opposition of 
February 1963, when the distance to Mars from Earth was over 100 million kilometers. 
Goldstein found Mars "a very difficult radar target because of its great distance from Earth 
and rapid rate of rotation." 12 

Mars defined the farthest limits of planetary radar detections until after the addition 
of the S-band radar to the Arecibo telescope and the X-band upgrade of the Goldstone 
Mars Station. Farther out, neither American nor Soviet efforts ever resulted in an unam- 
biguous radar detection of Jupiter. Certainly no echoes returned from any solid surface 
features. Nonetheless, US and Soviet investigators claimed detections. The case of Jupiter 
demonstrates the difficulty of obtaining radar echoes from a "soft" target, that is, one that 
is not a solid body, especially at such an extreme distance. 

Soviet investigators working with Vladimir Kotelnikov at the \evpatoriya radar center 
claimed to have detected radar echoes from Jupiter as early as September 1963 in the 29 
December 1963 issue of Pravda. The planet was in opposition at a distance of about 600 
million kilometers, six times farther than Mars at opposition in 1963. Not surprisingly, 
Kotelnikov and his colleagues reported that the echoes were weak. 13 

Between 17 October and 23 November 1963, during the same opposition of Jupiter, 
Dick Goldstein attempted observations of the planet with the Goldstone experimental 
radar. He found few if any echoes. Occasionally, though, a single run did indicate a "sta- 
tistically significant" return. Goldstein noticed that the time interval between these "sig- 
nificant" returns were most often a multiple of the rotation period of Jupiter, about 10 
hours. It seemed that a single localized area on Jupiter, which did not coincide with the 
celebrated red spot, was both a good and a smooth reflector of radar waves. 



10. Shapiro 30 September 1993; Peter Goldreich, Tidal De-spin of Planets and Satellites," Nature 208 
(1965): 375-376; Goldreich and Stanton Peale, "Resonant Spin States in the Solar System," Nature 209 (1966): 
1078-1079; Goldreich, "Final Spin States of Planets and Satellites," The Astronomical Journal 71 (1966): 1-7; 
Goldreich and Peale, "Spin-Orbit Coupling in the Solar System," The Astronomical Journal 7 1 (1966): 425-438. 
Also, in a joint paper, Peale and Gold attempted to explain the rotational period of Mercury in terms of a solar 
tidal torque effect. Peale and Gold, "Rotation of the Planet Mercury," Nature 206 (1965): 1241-1242. 

11. Shapiro 30 September 1993; Counselman, "Spin-Orbit Resonance of Mercury," Ph.D. diss., MIT, 
February 1969. See also Counselman, The Rotation of the Planet Mercury," Chapter 14, pp. 89-93 in R. G. 
Stern, ed., Review of NASA Sponsored Research at the Experimental Astronomy Laboratory (Cambridge: MIT, 1967). 

12. Goldstein and Willard F. Gillmore, "Radar Observations of Mars," Science 141 (1963): 1171-1172. 

13. Memorandum, O. Koksharova to I. Newian, 9 January 1964, translation of Pravda article, microfilm 
22-314, JPL Central Files. The article later appeared as Kotelnikov, Apraksin, Dubrovin, Kislik, Kuznetsov, Petrov, 
Rzhiga, Frantsesson, and Shakhovskoi, "Radar Observations of the Planet Jupiter," Soviet Physics-Doklady 9 ( 1964) : 
250-251. 



NORMAL SCIENCE 121 



To investigate further, Goldstein divided Jupiter into eight "time zones" and aver- 
aged all the runs which illuminated a single "time zone." The zone centered about the 
Jovian longitude 32 gave a response that Goldstein characterized as "statistically signifi- 
cant," although, he admitted, "this detection cannot be considered absolutely conclusive." 
The amount of return was simply too high to be believable. Goldstein later attempted to 
obtain echoes from Jupiter, using a Goldstone radar that was "a hundred times better," but 
he did not find any echoes. "We never were able to repeat it," he confessed. 14 

During the next oppositions of Jupiter, in November 1964, December 1965, and 
February 1966, Gordon Pettengill, Rolf Dyce, and Andy Sanchez, from the University of 
Puerto Rico at Rio Piedras, bounced radar waves off Jupiter using the 430-MHz Arecibo 
telescope. They designed their experiments to duplicate both the Soviet and JPL 
approaches; however, they failed to validate either the Soviet or JPL claims. 

The Arecibo investigators obtained results that were many times smaller than those 
reported by Goldstein. As for the Soviet results, which were close to the noise level, the 
Arecibo investigators concluded: 'The results reported in the U.S.S.R., which exceed the 
associated system noise by only 1.3 standard deviations of the fluctuations in that noise, 
should probably not be taken seriously." The Arecibo investigators suggested that the 
echoing mechanism was located in the upper levels of Jupiter's atmosphere "and that 
echoes might be returned only in exceptional circumstances." They concluded: "Many 
more observations of Jupiter spanning a long period of time and carried out at many wide- 
ly separated frequencies must be made before the behavior of Jupiter as a radar target can 
begin to be understood." 15 

Those observations never took place. Jupiter remained a misunderstood and disre- 
garded radar target. The outer reaches of planetary radar astronomy remained confined 
to the terrestrial planets. Jupiter and Saturn had to await the Arecibo S-band and the 
Goldstone X-band upgrades. Even then, however, planetary radar astronomers focused on 
solid targets, Jupiter's Galilean moons and Saturn's rings. 

Icarus Dicarus Dock 

In contrast to the attempts on Jupiter, the radar detection of Icarus was unambigu- 
ous. Icarus is an Earth-crossing asteroid, meaning its orbit around the Sun crosses that of 
Earth. On occasion, Icarus comes within 6.4 million kilometers of Earth, as it did in June 
1968. Nonetheless, Icarus was a difficult radar target, because of its small size. Its radar 
detectability was extremely small, one thousandth that of Mercury at its closest approach 
and only 10" 12 (one trillionth) that of the Moon. 16 

Only Haystack and the Goldstone Mars Station succeeded in detecting the asteroid. 
Although Icarus was within the declination coverage of Arecibo, attempts on 15 and 16 
June 1968 yielded ambiguous results. "A successful search would have been more likely," 
Rolf Dyce reported, "if the full performance of the line feed had been available." 17 

Investigators at Haystack Observatory leaped over imposing hurdles to make the first 
radar detection of Icarus. Irwin Shapiro and his Lincoln Laboratory colleagues prepared 
an ephemeris based on 71 optical observations of Icarus between 1949 and 1967. Radar 
observation began in earnest at Haystack on the morning of 12 June 1968. Late that 



14. Goldstein 14 September 1993; Goldstein, "Radar Observations of Jupiter," Science 144 (1964): 
842-843. 

15. Dyce, Pettengill, and Sanchez, "Radar Observations of Mars and Jupiter at 70 cm," The Astronomical 
Journal72 (1967): Ill-Ill. 

16. Goldstein, "Radar Observations of Icarus," Science 162 ( 1968) : 903. 

17. Dyce, "Attempted Detection of the Asteroid Icarus," in AIO, Research in Ionospheric Physics, Research 
Report RS 74 (Ithaca: CRSR, 31 July 1968), pp. 90-91. 



122 TO SEE THE UNSEEN 



evening, the Haystack observers received a new set of optical positions from astronomer 
Elizabeth Roemer at the University of Arizona. Michael Ash, of Lincoln Laboratory Group 
63, immediately integrated the optical data into the radar ephemeris, and by midnight 
Haystack was observing with the new ephemeris. 

Despite these heroic efforts to organize an improved ephemeris, rain, which severe- 
ly attenuates X-band radar signals, bedeviled the observations. As a result, Haystack did 
not obtain a reasonably firm indication of an echo from Icarus until the afternoon of 13 
June. Another particularly successful run that evening confirmed the presence of an echo, 
and by the morning of 14 June success was certain. Haystack terminated observations the 
morning of 15 June. To achieve its results, the Haystack radar had operated non-stop for 
20 hours. Analysis of the data suggested that the radius of Icarus was between 0.8 and 1.6 
km. 

The effort to detect Icarus in spite of the rain and the difficult nature of the aster- 
oid as a radar target inspired Louis P. Rainville, a Lincoln Laboratory technician who par- 
ticipated in the observations, to compose the following poem: 18 

Anode to Icarus 
Icarus Dicarus Dock 
We worked around the clock 
For three straight days 
We aimed our rays 
And an echo showed on the plot. 

But as always, there's a woe 

The rain made a better show 

As bleary our eyes 

Stared at the skies 

We hoped that the clouds would go. 

Oh for the roar and yell 

And the glory for old double "L " 

If on that crucial day 

When it came and went away 

We'd had one more decibel! 

Now as Icarus speeds from our sphere 
These words are for all men to hear 
T'was a good show men! 

Let's try again 

In another nineteen years! 

And so this was to be our lot 
We hoped for more than we got 
But we beat the worst; 
Wediditfirstl 
Icarus Dicarus Dock 

EURICARUS! 



18. "Weekly Reports, 5/13/68-8/11/69," 36/2/AC 135, MITA. The results appeared as Pettengill, 
Shapiro, Michael E. Ash, Ingalls, Louis P. Rainville, Smith, and Melvin L. Stone, "Radar Observations of Icarus," 
Icarus 10 (1969): 432-435. 



NORMAL SCIENCE 123 



Although Rainville's verse implied a contest to detect Icarus, no such competition 
existed; notwithstanding the rain, the spin direction of the Earth would assure Haystack 
the first look at the asteroid. At JPL, Dick Goldstein also successfully detected Icarus on 
14- 16 June 1968. Goldstein used a bistatic radar; the Mars Station received signals from a 
newly-developed 450-kilowatt transmitter installed on a nearby 26-meter (85-ft) dish. 
Although the Goldstone transmitter had nearly twice the power of Haystack Observatory, 
it still received only weak echoes. 19 

Using optical methods, asteroid astronomers Tom Gehrels, Elizabeth Roemer, and 
others calculated values for the period and the direction of the spin axis of Icarus and 
found that it appeared to be a rough stony-iron body, nearly spherical, with nonuniform 
reflectivity over the surface and with a spin period of 2 hours and 16 minutes. Its radius, 
they calculated, was at least 750 meters, which was close to the low end of the Haystack 
estimate. Armed with these results, Goldstein then reinterpreted his radar data and con- 
cluded that the surface of the asteroid was rocky and varied in roughness. 20 

The detection of Icarus was an important achievement of planetary radar, the first 
detection of an asteroid. Icarus also served to bring together radar and optical planetary 
astronomers in a special symposium on Icarus organized by Gordon Pettengill and 
chaired by Arvydas Kliore. Held in Austin, Texas, on 10 December 1968, the symposium 
was part of the pre-inaugural meeting of the Division for Planetary Science (DPS) of the 
American Astronomical Society (AAS) . Appropriately, the symposium papers appeared in 
the journal of planetary science Icarus.^ 

The Icarus symposium was a pivotal moment for both planetary radar astronomy 
specifically and planetary astronomy in general. Previously, no organization dedicated 
exclusively to planetary astronomy existed. The AAS had approved the formation of the 
DPS only a few months earlier in August 1968. In 1973, the DPS opened its ranks to plan- 
etary scientists other than AAS members, such as chemists, geologists, and geophysicists, 
and the DPS endorsed Icarus as the primary publication for planetary research. Under the 
editorial direction of Carl Sagan, a champion of radar astronomy, Icarus began to solicit 
more articles in planetary astrophysics, as opposed to the earlier focus on celestial 
mechanics. 22 

The Icarus symposium typified the normal science paradigm of planetary radar 
astronomy in the 1960s. Activity centered on detecting a solar system object with a ground- 
based radar instrument and analyzing range and Doppler data to obtain information on 
orbital parameters and radii and related questions. Radar astronomers then presented 
these results to asteroid astronomers, echoing the fruitful joining of radar observers and 
astronomers that led to the discovery of the origin of meteors. 

The Planetary Ephemeris Program 

Starting in the 1960s, the raw data for the improvement of planetary ephemerides 
was provided by the accumulation of radar range and other data. Traditional observations 
of planetary positions involved only angular determinations, which provide a position in 
a two-dimensional plane (the sky). Radar added new dimensions with range and Doppler 
shift data and included the astronomical unit and the radii and masses of Mercury, Mars, 



19. Goldstein, "Icarus," pp. 903-904. 

20. T. Gehrels, E. Roemer, R. C. Taylor, and B. H. Zellner, "Minor Planets and Related Objects: 4. 
Asteroid (1566) Icarus," The Astronomical Journal 75 (1970): 186-195; J. Veverka and W. Liller, "Observations of 
Icarus: 1968," Icarus 10 (1969): 441-444; Goldstein, "Radar Observations of Icarus," Icarus 10 (1969): 430-431. 

21. "Editor's Introduction to: A Symposium on Icarus," Icarus 10 (1969): 429. 

22. Tatarewicz, pp. 122-123. 



1 24 TO SEE THE UNSEEN 



and Venus. JPL and Lincoln Laboratory undertook separate radar ephemerides pro- 
grams. 

The Lincoln Laboratory radar ephemerides program, known as the Planetary 
Ephemeris Program or PEP, had its roots in the anti-ICBM early warning systems. As a 
member of a Lincoln Laboratory task force charged with the early detection of incoming 
enemy ICBMs with radar, Irwin Shapiro became expert in the mathematics of deducing 
ballistic missile trajectories from radar observations. He wrote up his results in a Lincoln 
Laboratory report in early 1957. After the launch of Sputnik, the New York publishing 
house McGraw-Hill released Shapiro's report as a book in April 1958, because his ballistic 
missile techniques were applicable (with some modification) to satellite tracking. That 
book then became the basis for the JPL ephemeris program. 23 

Shapiro and the radar group at Arecibo worked very closely on gathering data for 
the Lincoln Laboratory planetary radar ephemerides. As Don Campbell explained, "He 
has always been our ephemerides person, and we provide him with input." 24 The close 
connection between the Arecibo and MIT Lincoln Laboratory groups resulted from the 
appointment of Gordon Pettengill of Lincoln Laboratory as trie first associate director of 
the Arecibo Ionospheric Observatory. Pettengill set up the program so that the Arecibo 
radar ephemerides would always come from the PEP group. 

Acquiring input for the PEP required extensive data taking that involved long hours 
of observations, often late at night. Don Campbell and Ray Jurgens, both graduate 
students at the time, did a lot of the work on Venus, Mars, and Mercury, under the super- 
vision of Rolf Dyce and Gordon Pettengill. Campbell remembered the Mars observations 
in particular: 25 

This involved a lot of late nights, unfortunately, because the Mars opposition was 
around midnight. Every time the radar system was used, you had to go up to the sus- 
pended platform and actually change the receiver over. Then you had to go up after you 
finished to change them over again. Since I was very much at the lowest end of the totem 
pole at the time, it was my job to get on the cable car, go up to the structure, dabble with 
the thing late at night, change the receivers, come back, then when we finished, go back 
up and change them again. I suppose in retrospect you think of it as painful, although 
at the time I don't remember being particularly worried about it. I probably thought it was 
fun initially, although there were a lot fewer fences and safety devices on the platform then 
than there are now. It was quite possible to fall right through the thing. 

The initial PEP calculations performed with the planetary radar data served to refine 
the astronomical unit. Shapiro, however, also saw the need to refine the planetary 
ephemerides and the planetary masses. "It was also clear to me," he explained, "that we 
should not do it the way astronomers did, that is, with analytical series expanded out to 
huge numbers of terms. It seemed to me that with computers, even with those available at 
that time, we should be able to do this numerically, integrating the equations of the 
motions of the planets, integrating the partial derivatives, and doing everything digital- 
ly.'^ 

The PEP required a large computer as well as an immense computer program. 
Today, the program has well over 100,000 Fortran statements. Computer programming, 



23. Shapiro, Prediction of Ballistic Missile Trajectories from Radar Observations (New York: McGraw-Hill, 
1958); Shapiro 4 May 1994. 

24. Campbell 9 September 1993. 

25. Campbell 7 December 1993. 

26. Shapiro 30 September 1993. 



NORMAL SCIENCE 125 



however, was not Shapiro's forte. "I am pretty much a computer ignoramus," he confessed. 
So he hired a summer student, Michael E. Ash, who was a Princeton graduate student in 
mathematics. After graduating from Princeton, Ash worked at Lincoln Laboratory for 
about twelve years before taking a position at MIT's Draper Laboratory. Ash was the chief 
architect of the PEP computer program. John F. Chandler, a graduate student of Shapiro, 
took over the PEP from Ash and worked on it for over twenty years. Chandler expanded 
its applications so that now, in the words of Shapiro, "it does everything but slice bread." 

Originally, PEP also analyzed optical observations of the Sun, Moon, and planets, 
including optical data from the U.S. Naval Observatory back to 1850. "I spent more time 
than I care to admit," Shapiro confessed, "transferring to machine-readable form all the 
optical observations recorded in history since 1750 of the Sun, Moon, and planets. In the 
end, I didn't think it was worth it. I never published our results, to Michael Ash's chagrin. 
We had this manuscript about so high [nearly seven and a half centimeters or three inch- 
es], but I could never find enough time to polish it to my satisfaction. History passed us 
by. That was the biggest unfinished task of my life. Michael Ash put in a lot of work on 
that, though not as much as I did. But the ball was in my court to finish it off, and I did 
not do it. So this is a guilt session." 27 

Today the PEP is a very complicated program that analyzes a variety of observations, 
including lunar laser ranging data. When he moved to Draper Laboratory, Michael Ash 
modified it for satellite and lunar work. It is still used in planetary radar and by 
astronomers at the Harvard-Smithsonian Center for Astrophysics. It can process pulsar as 
well as Very Long Baseline Interferometry (VLBI) observations. For a while, most of the 
pulsar observers in the world used the PEP; however, they shifted to the JPL ephemeris 
program in recent years. A lack of funding has left the PEP just able to keep up with the 
Arecibo ephemeris work. 

In contrast, JPL has had the manpower and funding to support it. JPL developed its 
radar planetary ephemerides to support NASA spacecraft missions. Today, the JPL plane- 
tary ephemeris program, under the direction of E. Myles Standish, Jr., employs about a 
half dozen people who work on planetary, lunar, cometary, asteroidal, and satellite 
ephemerides. JPL initially called their ephemeris programs DE followed by the version 
number, with DE standing for "Development Ephemeris." In the late seventies, JPL sent 
over fifty copies of its ephemeris DE-96 to observatories, space agencies, and astronomical 
research groups around the world. 

Next came the DE-200 series, which used a new equator and equinox. All major 
national almanac offices, including the U.S. Naval Observatory, and the French, British, 
German, Japanese, and Russian almanac offices, now use the JPL DE-200 ephemeris pro- 
gram, as do many universities, the European Space Agency, and radio astronomers. 
Moreover, the DE-200 program, formerly available on magnetic tape, now is distributed 
through the Internet as an FTP file. 28 

The Lincoln Laboratory and JPL planetary ephemeris programs were uses of plane- 
tary radar data that did not necessarily lead to publications. Moreover, the vast amount of 
data routinely collected by radar astronomers and stored in the data bases of those 
ephemeris programs did not result from experiments designed to achieve a special pur- 
pose. Many planetary radar experiments quickly became routine operations. A glance at 
the extant Haystack radar log books indicates that radar astronomers rarely ran experi- 
ments themselves; expert technicians, like Haines Danforth and Lou Rainville, operated 



27. Shapiro 30 September 1993. 

28. Shapiro 30 September 1993; Shapiro 4 May 1994; E. Myles Standish, Jr., telephone conversation, 
20 May 1994; Paul Reichley, telephone conversation, 19 May 1994; Memorandum, Standish to R. Green, 10 May 
1979, Jurgens materials. 



1 26 TO SEE THE UNSEEN 



the radar equipment, and the software consisted of "cookbook programs." 29 This rou- 
tinization of experimentation is one aspect of Kuhnian "normal" or paradigm science. 

Testing Albert Einstein 

According to Shapiro and his colleagues at Lincoln Laboratory, the main purpose in 
gathering radar data for the planetary ephemeris program was "to test Einstein's theory 
of General Relativity." 30 The Shapiro test of the gravitational time delay predicted by 
General Relativity is interesting for its contribution to theoretical physics and astrophysics, 
as well as a major early achievement of planetary radar. Its development underscores the 
close and necessary connection between the capabilities of radar instruments and the 
kinds of scientific problems that one can solve with radar. It also illustrates the emotional 
intensity with which scientists struggle to assert their claims of discovery and priority of 
publication. 

After announcing his theory of Special Relativity in 1905, Albert Einstein spent 
another ten years developing the theory of General Relativity. 31 The theory of General 
Relativity traditionally has found support in three principal experimental areas. The first 
came from its accounting for the precession of Mercury's perihelion, the point at which 
Mercury is closest to the Sun. Traditional theoretical physics had been incapable of 
explaining the precession of Mercury's perihelion without leaving certain discrepancies 
unexplained. The ellipse of Mercury's orbit was turning faster than traditional physics said 
it ought to by an amount of some 43 seconds of arc per century. Einstein found that his 
equations gave just that amount of deviation from the measure predicted by traditional 
physics. The perihelion motion came out not only with the right numerical value but also 
in the correct direction. 

Einstein's theory of General Relativity predicted that a gravitational field would bend 
or deflect the path of light rays. For a light ray glancing the Sun, the theory of General 
Relativity predicted a deflection of 1.7 seconds of arc, about 1/1,000 of the angular width 
of the Sun as seen from the Earth. The theory of General Relativity also predicted that the 
gravitational field would cause the speed of a light wave to slow. 

Three types of experimental tests conducted over several decades confirmed the pre- 
cession of Mercury's perihelion, the deflection of light rays in a strong gravitational field, 
and the red shift. Consequently, Irwin Shapiro called his the Fourth Test of General 
Relativity. Initially, Shapiro was interested in using radar to confirm the precession of 
Mercury's perihelion. He hit upon that idea in 1959, but Shapiro was not sure whether a 
check on a widely accepted physical theory would be a worthwhile experiment. So in April 
1960, he asked a visiting French physicist, Cyrano de Dominicis, about the experiment. 



29. Hine 12 March 1993; Log books, Haystack Planetary Radar, HR-70-1, 9 December 1970 to 1 1 August 
1971; HR-71-1, 16 August 1971 to 14 April 1972; HR-73-1, 27 June 1973 to 26 November 1973; and HR-73-2, 9 
December 1970 to 11 August 1971, SEBRING. There is a lacuna in the log book records; observations made after 
14 April 1972 and before 27 June 1973 are not represented. 

30. Ash, Shapiro, and Smith, "Astronomical Constants and Planetary Ephemerides Deduced from 
Radar and Optical Observations," The Astronomical Journal 72 (1967): 338. 

31. The section on Einstein's general theory of relatively draws loosely from Banesh Hoffmann, 
Relativity and its Roots (New York: W. H. Freeman and Company, 1983); Peter G. Bergmann, The Riddle of 
Gravitation, revised and updated (New York: Charles Scribner's Sons, 1987); and Mendel Sachs, Relativity in Our 
Time: From Physics to Human Relations (Bristol, PA: Taylor and Francis, 1993) . See also Klaus Hentschel, "Einstein's 
Attitude towards Experiments: Testing Relativity Theory, 1907-1927," Studies in History and Philosophy of Science 23 
(1992): 593-624. 



NORMAL SCIENCE 127 



Dominicis told Shapiro he thought the experiment worth doing, because scientists had so 
few tests of relativity. 32 

No radar at the time, however, had the necessary sensitivity to carry out the preces- 
sion experiment. At any rate, the Fourth Test was not to measure the precession of 
Mercury's perihelion, but the slowing down of light waves caused by solar gravity. The new 
idea came to Shapiro in the spring of 1961, as he was attending a briefing for the military 
on some of the research conducted at Lincoln Laboratory and MIT with Department of 
Defense funds. After his lecture on measuring the speed of light, George Stroke, in a con- 
versation with Shapiro, mentioned that the speed of light is not the same everywhere, but 
depends on the gravitational field through which it is passing. Shapiro was surprised. He 
refreshed his memory on General Relativity and realized that there was a misunderstand- 
ing: according to General Relativity, a (freely) falling observer would measure at any 
location the same speed of light, independent of the (local) gravitational field. However, 
Shapiro reasoned, the effect of the gravitational field on the speed of light would be 
cumulative over a round-trip path (unlike the red shift) and that a radar experiment, 
therefore, ought to be able to detect this gravitational time delay. 

Shapiro now had the idea of testing the gravitational time delay predicted by General 
Relativity, but he realized that extant radars could not measure this small relativistic effect. 
Moreover, Shapiro did not write up the idea at that time. "I just kept it in the back of my 
mind," he explained. 33 

The inauguration of the Arecibo Ionospheric Observatory in November 1963 
revived Shapiro's interest in testing General Relativity. In July 1964, Shapiro and his wife, 
pregnant with their first child, travelled to Arecibo at Gordon Pettengill's invitation to 
spend the summer working at the AIO. When Charles Townes, then MIT Provost, visited 
Arecibo that summer, Shapiro briefed him on his proposed relativity test and told him 
that Arecibo could not perform the test. "We would never be able to see this effect," 
Shapiro explained. "The plasma effect of the solar corona would be of the same general 
type, and the variations would be much larger than the relativistic effect we were looking 
for. We would never be able to pick it out." 34 

Shapiro then returned home and learned that Haystack was to be dedicated in 
October 1964. Suddenly it occurred to Shapiro that Haystack might have enough capa- 
bility to do the experiment. He did some quick back-of-the-envelope calculations and con- 
cluded that Haystack might be able to do the experiment. Shapiro sent his manuscript to 
Physical Review Letters, and the journal received it on 13 November 1964. 35 

From his realization that Haystack could do the experiment to his submission of the 
paper took only one week. After doing the calculations more accurately, Shapiro realized 
that the sensitivity of the Haystack radar was not good enough to detect the relativistic 
effect. He and his Group Leader then requested an upgrade of the Haystack radar from 
the head of Lincoln Laboratory, Bill Radford, who subsequently obtained a funding 



32. Shapiro's recounting of the conception of the Fourth Test is included here, because the three- 
decade-long feud that resulted from it has become a part of the lore of radar astronomy. The sources for 
Shapiro's and Muhleman's versions of the story are oral histories conducted specifically for this history, namely 
Shapiro 1 October 1993 and Muhleman 19 May 1994. Paul Reichley, in a telephone conversation of 19 May 1994, 
refused any other comment than to state that he agreed with whatever Muhleman said. 

33. Shapiro 1 October 1993. 

34. Shapiro 1 October 1993. 

35. Shapiro, "Fourth Test of General Relativity," Physical Review Letters 13 (28 December 1964): 789. 
Although little noted at the time, Shapiro in his 1964 paper also pointed out that a possible change with 

atomic time of Newton's universal gravitational constant could be tested with radar observations of Mercury. 
Such a change was predicted by Paul Adrien Maurice Dirac in 1937 in his "large numbers hypothesis." Evidence 
for such a change is being actively sought still from monitoring orbits, as Shapiro suggested, because any such 
change would have profound effects on the evolution of the universe and the formation of structure within it. 



1 28 TO SEE THE UNSEEN 



commitment from the Rome Air Development Center for the upgrade. The upgrade 
consisted of design and construction of a new electronic plug-in unit, boosting the 
continuous-wave transmitter from 100 to 500 kilowatts, and replacement of the cooled 
parametric amplifier with a lower noise maser. 36 

In January 1965, as the design and construction of the radar upgrade was underway, 
a colleague showed Shapiro aJPL internal publication dated 31 October 1964 in which an 
article by Duane Muhleman discussed using radar to measure the general relativistic 
effect. 37 Shapiro was upset. He recalled vividly that in January 1964, he was walking near 
Harvard Square with Muhleman. When Muhleman asked him why he was still interested 
in radar astronomy, Shapiro told him about his idea to test this new effect predicted by 
General Relativity. Yet Muhleman did not acknowledge that conversation in his JPL 
report. Furthermore, that report only discussed the test being done near the inferior con- 
junction of Venus, where such a test was, and remains, infeasible. Shapiro noted that sev- 
eral years later, he approached Muhleman 's co-author of the JPL report, Paul Reichley, 
and asked him how he got involved in that project. To Shapiro's amazement, Reichley 
responded directly that Muhleman had said to him, "Shapiro says there's an effect here, 
let's look into it." 

The Muhleman and Shapiro relativity experiments both involved using radar and 
finding the relativistic time delay, but the design of their experiments differed widely. The 
Shapiro Test sent radar waves from Earth to graze past the Sun and bounce from Mercury 
(or Venus) at superior conjunction, that is, as the planet was just going behind the Sun 
(or emerging from behind the Sun) when seen from Earth. 

The radar waves then returned from Mercury (or Venus) and again passed near the 
Sun on their return trip to Earth. The Sun's gravitational field would slow down or delay 
the radar waves. General Relativity predicted that the cumulative time delay due to the 
direct effect of the Sun's gravitational field might be somewhat more than 200 microsec- 
onds. On the other hand, this time delay for radar waves bounced from, say, Venus at its 
inferior conjunction amounted to only about 10 microseconds. 38 

Muhleman 's experiment grew out of his theoretical work at JPL on communications 
with spacecraft flying near the Sun. Spacecraft navigation was at that time essentially a 
matter of measuring Doppler shift to a high degree of accuracy. Because JPL also was con- 
sidering ranging systems, Muhleman was studying the effects of the solar corona on both 
Doppler and range signals. "While working on that problem," he explained, "I realized 
that the main effect of the solar corona on the radio signal was that the signal was bent as 
it went around the Sun." Muhleman considered the solar gravitational field as though it 
were a lens with an index of refraction, an idea he later discovered in various relativity 
books. On a practical level, the Muhleman and Shapiro relativity studies differed widely. 
Whereas Shapiro intended to bounce radar waves off Mercury (or Venus) at superior con- 
junction, Muhleman proposed measuring at inferior conjunction, when the relativistic 
effect would not be detectable. 39 



36. C. Robert Wieser to Gen. B. A. Schriever, 31 May 1966, 13/56/AC 1 18, MITA. 

37. See Shapiro, "Fourth Test," pp. 789-791; Muhleman and Reichley, "Effects of General Relativity on 
Planetary Radar Distance Measurements," in Supporting Research and Advanced Development, Space Programs 
Summary 37-29 (Pasadena: JPL, 31 October 1964), pp. 239-241. Although Muhleman's note had an earlier pub- 
lication date, it was in an internal report with a tightly limited distribution, whereas Shapiro published in a wide- 
ly distributed scientific journal. Paul Reichley, Muhleman's co-author, was a young college graduate recently 
hired at JPL and worked with Muhleman on occultation studies of radio signals. Reichley, telephone conversa- 
tion, 19 May 1994; and Muhleman 19 May 1994. 

38. Shapiro, Effects of General Relativity on Interplanetary Time-Delay Measurements, Technical Report 368 
(Lexington: Lincoln Laboratory, 18 December 1964), pp. 1-2; and Shapiro, Testing General Relativity with 
Radar," Physical Review 145 (1966): 1005-1010. 

39. Muhleman 19 May 1994; Shapiro 1 October 1993; Shapiro, Effects of General Relativity, p. 2. 



NORMAL SCIENCE 129 



The judgement of general texts is that Irwin Shapiro originated the Fourth Test. 40 
Muhleman, for a number of reasons, dropped out of radar astronomy for over twenty 
years. Shapiro and his Lincoln Laboratory coworkers eventually did perform the Fourth 
Test at Haystack during the superior conjunction of Mercury in November 1966. Haystack 
made subsequent measurements during the superior conjunctions of 18 January, 11 May, 
and 24 August 1967. The results confirmed General Relativity to an accuracy of about ten 
percent. 41 

Additional observations of Mercury and Venus made at both Haystack and Arecibo 
during several superior conjunctions helped to refine the Fourth Test results. Subsequent 
experiments carried out on spacecraft further improved the accuracy of the test. The best 
accuracy yet achieved was from a combined MIT and JPL experiment on the Viking mis- 
sion to Mars; it confirmed Einstein's theory of General Relativity to a tenth of a percent. 
The accuracy of the measurement of the relativistic effect had improved by an impressive 
factor of 100, or two orders of magnitude, in 10 years. 42 

A Shifting Paradigm 

The planetary radar research discussed up to this point shared a consensus on prob- 
lem-solving activities in a way typical of a Kuhnian paradigmatic science. Among the forces 
driving the evolution of planetary radar astronomy was the interaction between the two 
kinds of problems radar astronomers attempted to solve. One set related to the larger the- 
oretical framework which the results of radar observations and analysis attempt to address; 
the other related to epistemological questions and included radar techniques. Because 
the two problem sets are necessarily linked to one another, the invention or adaptation of 
new radar techniques impacted on the kinds of scientific problems addressed by radar 
astronomy and, as a result, expanded the paradigm without altering the original problem- 
solving activities and techniques. 

One of the most powerful new radar techniques was planetary range-Doppler map- 
ping. It added a whole gamut of answers that radar astronomy previously could not 
provide. The successful application of the new technique depended on the availability of 
a generation of highly sensitive radars, Haystack, Arecibo, and DSS-14. Technology con- 
tinued to drive radar astronomy. Because the kinds of problems range-Doppler mapping 
solved were related more to geology than to astronomy, planetary radar grew close to the 
theoretical framework of planetary geology. This shift of the paradigm (without alteration 
of the original astronomy-oriented paradigm) also reflected the evolving social context of 
planetary radar, which in 1970 found itself a patron in NASA and its missions of planetary 
exploration. Thus, changing problem sets and theoretical frameworks on the one hand 
and the evolution of financial and institutional patronage on the other became inextrica- 
bly linked. 

Planetary Range-Doppler Mapping 

Both range and Doppler were standard radar measurements long before they 
united to provide range-Doppler maps of planetary surfaces. Range or time-delay 



40. See, for example, Peter G. Bergmann, The Riddle of Gravitation, rev. ed. (New York: Charles Scribner's 
Sons, 1987), p. 158. 

41. Shapiro 1 October 1993; Shapiro, Pettengill, Ash, Stone, Smith, Ingalls, and Brockelman, "Fourth 
Test of General Relativity: Preliminary Results," Physical Review Letters 20 (1968): 1265-1269. 

42. Shapiro 1 October 1993. 



1 30 TO SEE THE UNSEEN 



measurements determine how far away a target is by the amount of time the echo takes to 
return to the radar receiver. The greater the distance to the target, the longer the echo 
takes to appear in the receiver. Conversely, the shorter the distance to the target, the less 
time the echo takes to appear in the receiver. Knowing that radar waves travel at the speed 
of light, one can calculate the distance traveled by a radar signal from the amount of time 
between transmission of a radar signal and reception of its echo. 

If one assumes that a planetary target is a perfect sphere, then when a transmitter 
directs radar waves at it, the waves arrive first at a circular area at the center of the planet 
as viewed from Earth. The point on the planet's surface that has the radar at its zenith, 
and is thus closest to the observer, is called the subradar point. Thus, the radar waves first 
hit a circular area on the planet surrounding the subradar point and form what is called 
a range ring. Within each range ring, the distance from Earth to the planet's surface, that 
is, the range or delay in time, is the same. The longest delays (and therefore ranges) gen- 
erally correspond to echoes from near the planetary limbs. 

When a radar transmits, it sends a signal that contains only a very narrow band of fre- 
quencies and appears almost line-like. Such would be the case, too, for the echo received 
back at the radar were there no difference in the relative motion between the radar and 
its target. In reality, when looking from the Earth at a planetary target, this relative motion 
is always a factor. The combined motions of the Earth as it spins on its axis and orbits 
around the Sun, and of the planetary target as it also spins on its axis and orbits about the 
Sun, cause what is known as the Doppler effect or Doppler shift, which is the difference 
between the frequencies of the radar transmission and the radar echo. The differences in 
the relative motions of the radar and the target broaden the frequency of the returning 
signal. Instead of a (nearly) single frequency, the returning signal exhibits a spectrum of 
frequencies "shifted" or set off from the transmitted frequency. 

In order to remove the Doppler shift caused by the relative motion of the observer 
and the target, planetary radar astronomers generally use a radar ephemeris program. 
The program automatically adjusts the incoming signal for the expected Doppler shift, 
which itself changes over time because of the changes in relative motion of the observer 
and the target. Thus, the predicted Doppler shift must be accurate enough to avoid 
smearing out the echo in frequency. This requirement places stringent demands on the 
quality of the observing ephemeris. Thus, the Lincoln Laboratory PEP and the JPL 
Development Ephemeris series were of vital importance to the successful execution of 
planetary range-Doppler mapping. 

A given portion of the echo frequency spectrum corresponds to a slice or strip on 
the planet's surface. Each slice is parallel to the plane containing the line from the observ- 
er to the planet and the spin axis of the planet, and each slice has the same Doppler shift 
value, because each portion of that slice of the planet's surface has the same motion rela- 
tive to the observer. When Doppler shift and range data are combined, the slices of equal 
Doppler shift intersect the range rings to form "cells." In general, each range-frequency 
cell corresponds to two particular areas on the planet's surface. The amount of surface 
area corresponding to a particular range-frequency cell represents the resolution of the 
radar image on the planet's surface and varies over the planetary surface (see Technical 
Essay, Figure 42). 

The amount of power returned from the target for each range-frequency cell can be 
converted into a twoniimensional image of the planetary surface through a series of com- 
plex mathematical manipulations. Each spectrum has the attributes of power, bandwidth 
(the maximum spread of line-of-sight velocities) , shape, minor features, and a weak broad- 
band component. The total power received depends on such instrument factors as trans- 
mitter power, antenna gain, and pointing accuracy, as well as on the reflecting (backseat- 



NORMAL SCIENCE 131 



tering) properties of the target and the so-called radar equation. The radar equation 
states that the amount of power in an echo is inversely proportional to the fourth power 
of the distance. That means that the echo power received by a radar decreases sharply with 
increasing distance of the target. For instance, a radar echo is I/ 16th as strong if the dis- 
tance to the target is doubled, all other conditions being equal. 

In general, rough planetary surfaces backscatter more power from near the planet's 
limbs than a corresponding smooth sphere. Thus, a rough surface leads to a broadening 
of the frequency spectrum of the planetary echo. A smooth planetary surface (relative to 
the size of the wavelength of the radar waves) would broaden the return signal to a far less- 
er degree. The amount of power returned to the receiver in each resolution cell therefore 
corresponds to the planet's surface characteristics. 

The idea of combining range and Doppler data to form a radar image came 
together at Lincoln Laboratory in the late 1950s. There, Paul Green began to consider the 
calculation of a planet's spin velocity from a simultaneous measure of range and Doppler 
spread. Another member of the Lincoln Laboratory radar group, Roger Manasse, point- 
ed out that when you look at a spinning object, the planes of equal Doppler shift are 
parallel to the plane containing the line of sight and the rotation vector. 43 However, 
Manasse did not put the slices of Doppler shift together with the range rings. The origi- 
nator of that idea was Paul Green. 

Green remembers how the idea came to him: "I was sitting in my living room won- 
dering what the relationship was between the two of them. I also had noticed that Ben 
Yaplee had actually measured those things." 44 Ben Yaplee and others at the Naval 
Research Laboratory were using range rings to refine the Earth-Moon distance. They dis- 
covered that details in the structure of the return echoes could be correlated with lunar 
topography. 45 

However, they did not develop planetary radar range-Doppler imaging. "It was sim- 
ply an unevaluated measurement," Green explained. 'There was no attempt to know what 
deeper message might be behind that. I was just thinking, 'Hey! Wait a minute! That's 
kind of an interesting thing to do.' Maybe it was obvious, but might there not be some- 
thing deep behind it?" 46 

Soon after formulating range-Doppler mapping, Green discovered that classified 
military radar research at the University of Michigan had led to the conception of a simi- 
lar process but with significant differences. The military process involved imaging the 
Earth from aircraft and relied on developing a radar "history" of the target to create an 
image, while planetary range-Doppler mapping created a "snapshot" of a planetary sur- 
face from a ground-based radar. Because of the similarities in the two methods, Green was 
careful to call his planetary range-Doppler mapping. The University of Michigan radar 
effort, as we shall see in the next chapter, eventually had a profound impact on planetary 
radar astronomy. 

Paul Green first presented his ideas on range-Doppler mapping at the pioneering 
Endicott House Conference on Radar Astronomy, then at the URSI workshop on radar 
astronomy that followed immediately afterward in San Diego. An abstracted form of that 
paper and the others presented at the workshop soon appeared in the Journal of 
Geophysical Research. 47 



43. Roger Manasse, The Use of Radar Interferometer Measurements to Study Planets, Group Report 312-23 
(Lexington: Lincoln Laboratory, March 1957). 

44. Green 20 September 1993. 

45. See Ch. 1, note 69, and Ch. 3, note 14. 

46. Green 20 September 1993. 

47. Green 20 September 1993; Leadabrand, "Radar Astronomy Symposium Report," pp. 1111-1115. 
Earlier, a more complete exposition of the theory appeared as Green, A Summary of Detection Theory Notions in 
Radar Astronomy Terms, Group Report 34-84 (Lexington: Lincoln Laboratory, ISJanuary 1960). See, also, Ch. 3, 
note 22. 



132 



TO SEE THE UNSEEN 



Green did not apply his theory to actual radar mapping of the planets. Instead, it was 
his Lincoln Laboratory colleague Gordon Pettengill who used it beginning in 1960. 
Initially, Pettengill explored the surface of the Moon with the Millstone radar. The result 
was an image that barely resembled the lunar surface. Pettengill concluded, "It is obvious 
that much patient work lies ahead before detailed correlation with optical photographs 
may be attempted." 48 




Figure 16 

The first range-Doppler image of the Moon, 7 January 1960, made by Gordon PettengiU, using techniques developed by his 
Lincoln Laboratory colleague Paul Green. The top of the image (shown in range box 2) represents the point on the lunar sur- 
face closest to the radar. Pettengill, as the first associate director of the Arecibo Ionospheric Observatory, as it was then called, 
later guided range-Doppler imaging of the Moon and planets at Arecibo as well as at the Haystack Observatory. (Courtesy of 
MIT Lincoln Laboratory, Lexington, Massachusetts, photo no. 261209-1D.) 



48. Pettengill, "Measurements of Lunar Reflectivity Using the Millstone Radar," Proceedings of the IRE 48 
(May 1960): 933-934. 



NORMAL SCIENCE 133 



Lunar Radar Mapping 



Pettengill made a second attempt at lunar radar mapping in June 1961, again using 
the Millstone radar. Those and the previous Pettengill radar images had what radar 
astronomers call north-south ambiguity. The nature of range-Doppler mapping is to cre- 
ate an uncertainty (called north-south ambiguity), such that the observer does not know 
from which hemisphere the echoes are returning. The range-Doppler technique creates 
two points, one in the northern hemisphere and the other in the southern hemisphere, 
with exactly the same range and Doppler values. The radar data cannot distinguish the 
hemisphere of origin of the return echo and thus presents a confusing picture of the tar- 
get's features. 

Pettengill had no technique yet for distinguishing northern-hemisphere echoes 
from southern-hemisphere echoes. He knew that the youngest, and therefore the rough- 
est, large feature on the lunar surface visible from Earth was the crater Tycho. During a 
full Moon, this crater appears to have rays emanating across the lunar surface. When 
Pettengill looked at the echo spectra, he found anomalously high spikes that were consis- 
tent from run to run. He assumed that they were in the southern hemisphere (the loca- 
tion of Tycho) and found they matched the crater's location. 49 

For the first time, a lunar surface feature and a radar return had matched. However, 
the north-south ambiguity problem stood in the way of refining range-Doppler mapping 
into a useful tool for exploring the solar system. One solution appeared when the Arecibo 
Ionospheric Observatory began operation in November 1963. There, at the instigation of 
Pettengill, who was now Associate Director of Arecibo, Thomas W. Thompson, then a 
Cornell graduate student, and Rolf Dyce began range-Doppler mapping of the Moon. 

In contrast to Millstone, the Arecibo radar antenna had a narrow beamwidth relative 
to the angular size of the Moon. The Moon has a diameter of a half degree or 30 minutes 
of arc. The width of the Arecibo antenna beam was 10 minutes. Instead of aiming the 
antenna at the center of the lunar disk facing Earth, Thompson and Dyce aimed it at a 
point 10 minutes of arc south from the center. The Arecibo telescope received echoes, 
therefore, only from the lower or "southern" part of the Moon. The technique assuaged 
the problem of north-south ambiguity, but was applicable to only the Moon. Venus was 
only a speck, slightly more than one minute of arc, compared to the Moon's 30 minutes 
of arc. 50 

Using this approach, Thompson and Dyce explored eight regions of the lunar sur- 
face and collected data on echo strength. They converted the data into "contour" lines of 
relative reflectivity. Thompson placed these lines, computed and plotted on a transparent 
overlay, over lunar maps made from photographs. The resultant radar contour map had 
a resolution of 20 by 30 km. 51 

Thompson continued to carry out range-Doppler mapping of the Moon by taking 
advantage of the increasingly narrow beamwidth of the Arecibo antenna. By reducing the 
beamwidth from 10 to 7 minutes of arc, he succeeded in creating a range-Doppler map of 
the crater Tycho with surface resolutions between 7 and 10 km. The output from a given 
radar observation now represented a considerable quantity of data; between 10,000 (10 4 ) 
and 100,000 (10 5 ) values of intensity (or pixels) constituted a single map. 



49. Pettengill and John C. Henry, "Enhancement of Radar Reflectivity Associated with the Lunar Crater 
Tycho," Journal of Geophysical Research 67 (1962): 4881-4885. Pettengill's co-author was an MIT electrical engi- 
neering graduate student who used the experience in writing his master's thesis. Henry, "An Automated 
Procedure for the Mapping of Extended Radio Sources," M.S. thesis, MIT, 1965. 

50. Source for the arc measurement of Venus: Goldstein, "Radar Studies of Venus," in Audoin Dollfus, 
ed., Moon and Planets (Amsterdam: North-Holland Publishing Company, 1967), p. 127. 

51. Thompson 29 November 1994; Thompson and Dyce, "Mapping of Lunar Radar Reflectivity at 70 
Centimeters," Journal of Geophysical Research 7 1 (1966): 4843-4853. 



134 



TO SEE THE UNSEEN 




Figure 17 

Radar map of the lunar crater Tycho with a resolution of I kilometer made urith the 3.8-cm (7,750-MHz) Haystack 
Observatory radar. The grid lines are spaced about 17 km apart. (Courtesy of MIT Lincoln Laboratory, Lexington, 
Massachusetts, photo no. 242336-1.) 

At the same time, Gordon Pettengill guided lunar radar observations at Haystack, 
which had become available in late 1964. Haystack, moreover, had a narrower antenna 
beamwidth, only 3 minutes of arc, and the higher operating frequency of Haystack (3.8 
cm, X-band) compared to Arecibo (70 cm, UHF) helped Haystack to achieve a much finer 
resolution on Tycho: between 1 and 2 km. The Haystack radar images now approached 
the quality of lunar photographs made from Earth. In the words of Pettengill and 



NORMAL SCIENCE 135 



Thompson, 'The most immediately striking feature of the 3.8-cm [Haystack] observations 
is their resemblance to the optical photograph...." 52 

The coincidental refinement of lunar range-Doppler imaging and the commitment 
to place an American on the Moon before the end of the 1960s enhanced the value of the 
lunar radar work done at both Arecibo and Haystack. NASA Apollo mission staff used the 
radar images to help select landing sites, and Apollo funded Thompson's dissertation and 
subsequent radar studies of the Moon. Once the resolution of radar images surpassed the 
resolution of lunar photographs made from Earth, the value of lunar radar studies to 
NASA grew even more. Thus, the new technique brought radar astronomy closer to the 
scientific needs of NASA, increasingly the patron of radar astronomy. 

At Arecibo, Tommy Thompson and Rolf Dyce undertook radar mapping of the 
Moon at both 40 MHz (7.5 meters) and 430 MHz (70 cm) under a supplementary grant 
from NASA. A joint report with Lincoln Laboratory compared the Arecibo results with 
those carried out at Haystack by Stan Zisk with additional NASA funding under a contract 
between MIT and the Manned Spacecraft Center in Houston. NASA funded lunar studies 
at both telescopes until 1972, when the Apollo program came to an end. 53 



Venus Radar Mapping 



In 1964, as Thompson and Zisk were starting their lunar mapping activities, Roland 
Carpenter and Dick Goldstein analyzed spectra from Venus and discovered the first fea- 
tures on that planet's surface. The Goldstone Venus radar lacked sufficient sensitivity to 
apply range-Doppler mapping to Venus. However, once the Mars Station became avail- 
able, Goldstein continued his exploration of Cytherean surface features using range- 
Doppler techniques, but without resolving the north-south ambiguity. Thus began one of 
the most long-lived and extensive activities of planetary radar astronomers. This scientific 
niche for radar resulted from that planet's opaque atmosphere which barred exploration 
with optical methods. 

When Dick Goldstein observed Venus during the 1964 inferior conjunction, he 
looked only at the structure of the spectra returned from the planet. This was the same 
technique that Roland Carpenter had used earlier to discover the retrograde motion of 
Venus; it was not range-Doppler mapping. A few topographic features were visible as 
details in the return spectra. Goldstein found two features represented as peaks. They 
moved slowly across the spectrogram, a graph plotting echo power density versus fre- 
quency, from the high-frequency side to the low-frequency side, in synchronization with 
the planet's rotation. 

Goldstein then placed his two features on a coordinate system with the first feature, 
named Alpha (a) , located on his zero degree meridian in the southern hemisphere. The 
second feature, named Beta ((3), Goldstein placed in the northern hemisphere. His coor- 
dinate system was somewhat arbitrary out of necessity, as astronomers generally had not 
agreed upon any Cytherean coordinate system. Additional analysis of the 1964 data 
revealed three more features around the equator. Goldstein named them Gamma (i), 
Delta (8), and Epsilon (e). 



52. Thompson 29 November 1994; Pettengill and Thompson, "A Radar Study of the Lunar Crater 
Tycho at 3.8-cm and 70-cm Wavelengths," Icarus 8 (1968): 457-471, esp. 464. 

53. The research was conducted under NASA grant NGR-33-010-024. NEROC, Semiannual Report of the 
Haystack Observatory, 15 July 1972, p. ii. See, also, Ch. 4, note 15. 



136 



TO SEE THE UNSEEN 




Figure 18 

One of the earliest range-Doppler images of Venus made by Richard Goldstein ofJPL with the Goldstone radar. The notation 
"0" indicates the meridian in Goldstein 's coordinate system. Visible are the first surface features identified by Goldstein: Alpha 
(a), on the meridian in the southern hemisphere, Beta (0), in the far west of the northern hemisphere, and Delta (S), just to 
the north of Beta. Gamma (T) and Epsilon (E), two additional features identified by Goldstein, are not labelled. The radar 
names Alpha and Beta were retained when astronomers began naming the surf ace features of Venus. (Courtesy of Jet Propulsion 
Laboratory, photo no. 331-4849AA.) 



NORMAL SCIENCE 



137 



Although he judged that these features were probably mountain ranges, Goldstein had 
insufficient evidence. What were they? "Venus is still a mystery planet," Goldstein con- 
cluded. "However, it may no longer be viewed as featureless, but rather as an exciting 
object for further study." 54 

Using the data taken with the newly operational Mars Station during the 1967 Venus 
inferior conjunction, Goldstein studied the Beta region in more detail, attempting to 
determine its size and character, rather than searching for new features. The Mars Station, 
moreover, provided sufficient sensitivity to attempt range-Doppler mapping. Goldstein 
observed Beta, Delta, and an unnamed region at (his) 40 South latitude and made a 
crude radar image of the 6 region. Still, Goldstein lacked sufficient data to determine 
whether Beta was a mountain range or another type of feature. 55 




-40* 



-35 -30 

LONGITUDE 



-25' 



Figure 19 

A detailed radar view of the Beta region of Venus, 1967, made by Dick Goldstein ofJPL using the Goldstone radar. It exem- 
plifies the limits of resolution available in some of the earliest radar images of that planet. (Courtesy of Jet Propulsion 
laboratory, photo no. P-8882.) 



54. Goldstein, "Preliminary Venus Radar Results ," Journal of Research of the National Bureau of Standards, 
Section D: Radio Science 69D (1965) : 1623-1625; Goldstein, "Radar Studies of Venus," in Dollfus, Moon and Planets, 
pp. 126-131. This article also appeared as Goldstein, Radar Studies of Venus, Technical Report 32-1081 (Pasadena: 
JPL, 1967). 

55. Goldstein and Shalhav Zohar, "Venus Map: A Detailed Look at the Feature B," Nature 219 (1968): 
357-358; Goldstein, "A Radar View of the Surface of Venus," Proceedings of the American Philosophical Society 113 
(June 1969): 224-228. Goldstein's co-author, Shalhav Zohar, was a fellow JPL employee who developed much of 
the software used in the experiment. 



138 



TO SEE THE UNSEEN 



Meanwhile, Roland Carpenter, who was now both a JPL employee and an instructor 
in the Department of Astronomy of the University of California, Los Angeles, had ana- 
lyzed 1964 Venus inferior conjunction radar data. Carpenter found two distinct peaks in 
the return spectra that persisted day after day and moved slowly with time. On closer 
examination, the first peak appeared to have three components, which he hesitated to 
interpret because he felt their nature could not be determined with the available data. 

Using Goldstein's coordinate system, Carpenter began to identify the most pro- 
nounced features with letters of the alphabet from A to G. He labeled less probable loca- 
tions as numerical extensions of nearby features, e.g., Bl, Cl, C2, D2, and D3. 
Correlations between Carpenter's and Goldstein's features began to emerge. Carpenter's 
feature F had the same location as Goldstein's a, and Carpenter's group B, C, and D cor- 
responded to Goldstein's |3 (Table 2). 56 



Table 2 


Radar Features of Venus 




Goldstein 


Carpenter 


Haystack 


Arecibo 






Alpha 


F 


Haystack I 


Faraday 






Beta 


B 










Beta 


C 


Haystack IV 








Beta 


D 










Beta 




Haystack II 


Gauss 






Beta 




Haystack III 


Hertz 






Gamma 












Delta 


D2 


Haystack A 












(later Haystack VI) 








Epsilon 














A 












Bl 


Haystack B 










Cl 












C2 


Haystack V 










D3 












E 












G 














Haystack C 












Haystack D 














Maxwell 






Sources 






R.M. Goldstein, "Radar Studies of Venus," in Audoin Dollfus, ed., Moon and Planets (Amsterdam: North-Holland Publishing 






Company, 1967), pp. 126-131; R.M. Goldstein and H.C. Rumsey.Jr., "A Radar Snapshot of Venus," Science 169 (1970): 974-977; 
R.L. Carpenter, "Study ofVenus by CW Radar: 1964 Results," The Astronommljoumal 71 (1966): 142-152, especially pp. 148-151; 
A.E.E. Rogers, T. Hagfors, R.A. Brockelman, R.P. Ingalls, J.I. Levine, G.H. Pettengill, and F.S. Weinstein, A Radar Interferometer 
Study of Venus at 3. 8 cm, Technical Report 444 (Lexington: Lincoln Laboratory, 14 February 1968); A.E.E. Rogers, R.P. Ingalls, 
and G.H. Pettengill, "Radar Map of Venus at 3.8 cm Wavelength," /znu21 (1974): 237-241; D.B. Campbell, R.F. Jurgens, R.B. 
Dyce, F.S. Harris, and G.H. Pettengill, "Radar Interferometric Observations of Venus at 70-Centimeter Wavelength," Saence 






170 (1970): 1090-1092; R.F. Jurgens, "Some Preliminary Results of the 70-cm Radar Studies of Venus," Radio Sdence5 (1970): 
435-442- and R.F. Jurgens, A Study of the Average and Anamalous Radar Scattering from the Surface of Venus at 70 Cm 
Wavelength," PhD diss., Cornell University, June 1968, also published internally as CRSR Research Report no. 297 (Ithaca: 






CRSR, May 1968). 







Carpenter dropped out of radar astronomy and pursued a teaching career, while 
Goldstein continued to explore Venus. The 1969 inferior conjunction of Venus provided 
an opportunity to use range-Doppler mapping. Goldstein combined the 1969 data with ear- 
lier data, then applied a mathematical method devised by fellow JPL employee Howard C. 
Rumsey.Jr., which involved the construction of a large matrix of range and Doppler values. 

The mapping process divided the surface of Venus into small cells 1/2 square in lat- 
itude and longitude. A column vector (X) consisted of the unknown reflectivities of these 
cells, while a second column vector (S) contained all the processed data from 17 days of 



56. Carpenter, "Study of Venus by C\V Radar: 1964 Results," The Astronomical Journal 71 ( 1966) : 142-152, 
especially pp. 148-151. 



NORMAL SCIENCE 139 



observations. Already, Goldstein and Rumsey were dealing with a large amount of data; 
vector X had about 40,000 components, vector S about 120,000 components. They 
expressed the relationship between vectors S and X as the equation: 

AX = S, 

in which A was a matrix whose components could be computed from known parameters 
and the motion of Venus and Earth. Matrix A consisted of 120,000 by 40,000 components. 

As the authors wrote, "Obviously, we cannot compute every component of a matrix 
with over 10 9 entries." The matrix was "so big," Goldstein recalled, "that we couldn't even 
read it into the computer except one line at a time." 57 Despite the difficulty of handling 
the gargantuan matrix, Goldstein produced a number of somewhat unambiguous images 
of Venus. Once the 1969 data had been converted into a range-Doppler map, in which 
each resolution cell represented an area on the planet's surface, Goldstein made cumu- 
lative maps by adding earlier data. The north and south areas of the cumulative maps were 
similar, but not identical; however, the images suffered serious flaws, including the "run- 
way" strip running more or less along the planet's equator. Nonetheless, Goldstein 
succeeded in resolving a for the first time on a map. It was a roundish feature, about 
1,000 km across. 58 

Goldstein continued to map Venus with Rumsey's mathematical approach, adding 
data taken during the 1970 inferior conjunction to that acquired in 1969. The 1970 data 
were better, being less noisy, because the Deep Space Network had increased the trans- 
mitter power of the Goldstone Mars Station from 100 to 400 kilowatts. The total system 
noise temperature stood at a low 25 K. Regions a and B remained the dominant features 
of the JPL radar map. 59 

Meanwhile, at Arecibo and Haystack, radar astronomers were creating Venus images 
with their own techniques. At Arecibo, Cornell University doctoral student Rayjurgens, 
with support from an NSF Faculty Fellowship, undertook the analysis of radar data taken 
during the 1964 inferior conjunction. Dyce and Pettengill had made the radar observa- 
tions to supply the Planetary Ephemeris Program data base, not to make a range-Doppler 
map of Venus. 60 

In correlating the radar data with the Cytherean surface, Jurgens abandoned his own 
zero degree meridian in favor of a modified version of Carpenter's coordinate system that 
incorporated the latest pole position and rotation rate supplied by Irwin Shapiro from the 
PEP. Consequently, Goldstein's a and Carpenter's F were not at the zero meridian but 
closer to 5 longitude. Jurgens identified the features he found by latitude and longitude 
(e.g., 20,-102, in which "-" indicated South latitude or West longitude), then compared 
his features with those discovered by Goldstein and Carpenter. 

Jurgens gave particular attention to Goldstein's B region (Carpenter's group B, C, D, 
to which Jurgens added E), and he managed to locate most of Carpenter's features. In 
addition, Jurgens spotted a new feature near Goldstein's Beta. Borrowing from Tommy 
Thompson's lunar radar mapping work, Jurgens interpreted the feature as a ring struc- 
ture, specifically a crater, and argued that such a crater might be caused by meteoric 
impact. Jurgens admitted that "although the evidence for a ring structure is not as strong 
as one might desire, it at least raises the question of whether such structures would be 
expected on Venus." 61 Indeed, it was one of the first attempts to relate radar observations 
and geological interpretation. 



57. Goldstein 14 September 1993. 

58. Goldstein and Rumsey, "A Radar Snapshot of Venus," Science 169 (1970): 974-977. 

59. Goldstein and Rumsey, "A Radar Image of Venus," Icarus 17 (1972): 699-703. 

60. Jurgens 23 May 1994. 

61. Jurgens, "A Study of the Average and Anomalous Radar Scattering," pp. 71 and 87-1 10. 



140 



TO SEE THE UNSEEN 



Before completing his dissertation, Jurgens observed Venus during the 1967 inferior 
conjunction, when the Arecibo antenna had an improved receiver system, better data 
acquisition procedures, and a lower receiver noise temperature. Jurgens combined the 
1967 data with additional observations made during the subsequent 1969 conjunction. In 
order to mitigate the north-south ambiguity problem, he compared observations made a 
few weeks apart, thereby taking advantage of the changing Doppler geometries between 
Earth and Venus. 

Jurgens continued to explore the (3 region, in particular, as well as new areas of the 
planet's surface. On the urging of Tommy Gold, he named his features after scientists 
famous for their work in electromagnetism: Karl Friedrich Gauss (1777-1855), Heinrich 
Rudolph Hertz (1857-1894), Michael Faraday (1791-1867), and James Clerk Maxwell 
(1831-1879). Gauss and Hertz both corresponded strongly to Goldstein's |3 region. 
Faraday was Goldstein's a. However, Maxwell, discovered during the 1967 conjunction, 
had no match among previous citings of Cytherean surface features. 62 It was an original 
and enduring contribution to Venus mapping. 




Figure 20 

Ray Jurgens discovered a new Venus surface feature, named Maxwell, from these range-Doppler images made at the Arecibo 
Observatory on 4 September 1967 during inferior conjunction. The bright spot at the leading edge of the image is the subradar 
point, while the spot closest to the subradar point is the Beta region. Maxwell is the spot farther from the planet's leading edge. 
(Courtesy of Ray Jurgens.) 



62. Jurgens, "Some Preliminary Results of the 70-cm Radar Studies of Venus," Radio Science 5 (1970): 
435-442; AIO, Research in Ionospheric Physics, Research Report RS 74 (Ithaca: CRSR, 31 July 1968), pp. 84-85. 



NORMAL SCIENCE 141 



Investigators at Haystack Observatory also observed Venus during the 1967 conjunc- 
tion, but they used a unique technique they pioneered called radar interferometry. It 
resolved the problem of north-south ambiguity in a superior fashion. An optical 
interferometer is an instrument for analyzing the light spectrum by studying patterns of 
interference, that is, how lightwaves interact with each other. Martin Ryle and other radio 
astronomers had been designing interferometers since the late 1950s. These radio inter- 
ferometers used two or more radio telescopes arranged along a straight line (called the 
base line) and allowed astronomers to "synthesize" observations at higher resolutions than 
possible with a single antenna. 63 

The inventor of the radar interferometer was Alan E. E. Rogers, then an electrical 
engineering graduate student at MIT. MIT Prof. Alan H. Barrett was recruiting students 
to participate in his radio astronomy work on the newly discovered OH spectral line. Alan 
Rogers joined him and did his masters and doctoral theses on the OH line. As part of his 
doctoral thesis research, Rogers helped to develop a radio interferometer that linked the 
Millstone and Haystack radars. 

After graduating and spending a year home in Africa, Rogers returned to Lincoln 
Laboratory, where he was hired to work in the radar group with Gordon Pettengill. 
Although trained as a radio astronomer, Rogers rapidly became absorbed in planetary 
radar work and proposed a radar interferometer to eliminate the problem of north-south 
ambiguity that was typical of range-Doppler mapping. 64 This was not the first time that a 
radar astronomy technique derived from radio astronomy. 

The X-band (7,840 MHz; 3.8 cm) radar interferometer linked the Haystack and 
Project Westford antennas, which are 1 .2 km apart, in the so-called Hayford configuration. 
In the interferometry experiments, Haystack transmitted a continuous-wave signal to 
Venus, and both the Haystack and Westford antennas received. Technicians working 
under Dick Ingalls of Haystack reduced and analyzed the echoes to create a range- 
Doppler map. The size of the resolution cell on the planet's surface was about 150 km 
square. 



63. See Bracewell, "Early Work on Imaging Theory," pp. 167-190 and Schcucr, "Aperture Synthesis at 
Cambridge," pp. 249-265 in Sullivan. 

64. Rogers 5 May 1994. 



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TO SEE THE UNSEEN 




Figure 21 

One of the first range-Doppler images of Venus made with a radar interferometer, the Haystack and Westford antennas in 
tandem, in 1967. Not only are the Alpha and Beta regions discernible, but the complexity of Beta is revealed. (Courtesy of Alan 
E. E. Rogers.) 

Next, Rogers and Ingalls combined the signals from the two antennas to obtain the 
fringe amplitude and phase for each range-Doppler cell. In an elaborate computer 
procedure, they rotated the fringe pattern so that the lines of constant phase were normal 
to the axis of apparent rotation of the planet. The lines of constant phase now were 
perpendicular to the slices of equal Doppler value. Although each pair of resolution cells 



NORMAL SCIENCE 143 



that exhibited north-south ambiguity had the same range and Doppler shift values, one 
could distinguish the north and south cells because they had opposite phases. 65 

One of the first applications of this radar interferometer was to the lunar work being 
carried out at Haystack for the NASA Manned Spacecraft Center by Stan Zisk. The lunar 
topographic maps that Zisk created with the Hayford interferometer were carried out 
under the name "Operation Haymoon" until December 1972, when the Apollo mission 
ended. 66 Tommy Thompson carried out a similar interferometric study of the Moon using 
the 40-MHz (7.5-meter) radar at Arecibo. 

Alan Rogers and Dick Ingalls also studied Venus during the 1967 inferior conjunc- 
tion with the Hayford interferometer and identified eight surface regions. Just as each 
previous radar astronomer had invented his own nomenclature, they labeled features with 
Roman numerals and letters. The features of which they were certain became Haystack I 
through Haystack IV. The probable regions were Haystack A through Haystack D. Five of 
these eight regions corresponded to features already observed by either Goldstein or 
Carpenter. Haystack I appeared to be Goldstein's a and Carpenter's F, while Haystack II 
matched Goldstein's 6 (Table 2). Jurgens' Arecibo results had not yet been published. 67 

Alan Rogers and Dick Ingalls then published a map of Venus showing the correlation 
of Haystack and JPL features in a 1969 issue of Science. The B region now appeared to be 
large and complex. The Hayford radar interferometer confirmed and extended the 
observations of Goldstein and Carpenter. With interferometer data taken during the 1969 
and 1972 conjunctions using an instrument with a lower system noise temperature, Alan 
Rogers and Dick Ingalls refined their map of Venus; the data continued to indicate agree- 
ment among the Haystack and JPL features. 69 

The waxing tide of links between Lincoln Laboratory and Arecibo set in motion by 
the appointment of Gordon Pettengill as associate director of Arecibo facilitated the trans- 
planting of radar interferometry to Arecibo. In fact, investigators at Arecibo built two 
additional antennas to study the Moon and Venus with the new technique. The lunar 
interferometer used the 40-MHz antenna, while the planetary radar interferometer used 
the 430-MHz antenna. NASA continued to underwrite Tommy Thompson's lunar radar 
work through a supplementary grant. 70 



65. For a description of the radar interferometer, see Rogers, Hagfors, Brockelman, Ingalls, Levine, 
Pettengill, and Weinstein, A Radar Interferometer Study of Venus at 3.8 cm, Technical Report 444 (Lexington: 
Lincoln Laboratory, 14 February 1968). 

66. Rogers 5 May 1994; Documents in 44/2/AC 135; "Haystack Operations Summary, 
8/11/69-5/18/70," 37/2/AC 135; "Funding Proposal, "Programs in Radio Astronomy at the Haystack 
Observatory," NSF, 10/1/72-9/30/73," 28/2/AC 135, MITA; NEROC, Semiannual Report of the Haystack 
Observatory, 15 July 1972, p. ii; NEROC, Final Progress Report Radar Studies of the Planets, 29 August 1974, p. 1. A 
number of techniques for extracting lunar topography from interferometric data were devised. Delay-Doppler 
stereoscopy was developed by Irwin Shapiro and independendy by Thomas Thompson and Stan Zisk. Anodier 
technique, called delay-Doppler interferometry, was suggested by Shapiro and developed by Zisk and Rogers; 
Thompson pointed out the strength of the Hayford interferometer for this application. Shapiro, Zisk, Rogers, 
Slade, and Thompson, "Lunar Topography: Global Determination by Radar," Science 178 (1972): 939-948, esp. 
notes 19 and 21, p. 948. 

67. Thompson, "Map of Lunar Radar Reflectivity at 7.5-m Wavelength," Icarus 13 (1970): 363-370. 

68. Brockelman, Evans, Ingalls, Levine, and Pettengill, Reflection Properties of Venus at 3.8 cm, Report 456 
(Lexington: Lincoln Laboratory, 1968), especially pp. 34-35, 44, and 49-50; Rogers and Ingalls, "Venus: 
Mapping the Surface Reflectivity by Radar Interferometry," Science 165 (1969): 797-799. 

69. Rogers and Ingalls, "Radar Mapping of Venus with Interferometric Resolution of the Range-Doppler 
Ambiguity," Radio Science 5 (1970): 425-433; Rogers, Ingalls, and Pettengill, "Radar Map of Venus at 3.8 cm 
Wavelength," Icarus 21 (1974): 237-241. 

70. AIO, Research in Ionospheric Physics, Research Report RS 75 (Ithaca: CRSR, 31 March 1969), pp. 2 and 
11-12; Annual Summary Report, Center for Radiophysics and Space Research, July I, 1968 June 30, 1969, 30 June 1969, 
p. 4. 



144 



TO SEE THE UNSEEN 







Figure 22 

Diagram of Venus surface features made with the Haystack-Westford interferometer. Features observed with the Haystack- 
Westford interferometer are indicated variously by capital letters, Roman numerals, and coordinate numbers. Goldstein 's Alpha 
and Beta regions are indicated (Region a and Region ft), while the labels given by Carpenter are shown in parentheses. 
(Courtesy of Alan E. E. Rogers.) 



NORMAL SCIENCE 



145 




Figure 23 

The antenna built by Areribo Observatory employee and radio amateur Sam Harris and located at Higuillales about 10 km 
from the main dish. Harris and his antenna are a reminder of the important role self-taught engineers and radio amateurs 

have played in the design and construction of scientific instruments, particularly in the field of astronomy. (Courtesy of Ray 
Jurgens.) 



Undertaking radar interferometric observations of Venus at Arecibo was Cornell 
graduate student Don Campbell. Campbell came to Cornell from Australia, his native 
country, where he had studied radio astronomy at the University of Sydney, though not 
through the agreement between the two universities. 71 His observations of Venus in 1969 
with the radar interferometer formed the basis of his doctoral thesis. Located about 10 km 
from the Arecibo Observatory at Higuillales near Los Canos, the auxiliary interferometer 
antenna was a square parabolic section, 30 meters by 30 meters (100 ft by 100 ft) with a 
movable offset feed that allowed tracking up to 10 from the zenith. 72 



71. Campbell 7 December 1993. 

72. Donald B. Campbell, "Radar Interferometric Observations of Venus," Ph.D. diss., Cornell, July 1971; 
AIO, Research in Ionospheric Physics, Research Report RS 75 (Ithaca: CRSR, 31 March 1969), pp. 12-13; Campbell, 
Jurgens, Dyce, F. Sam Harris, and Pettengill, "Radar Interferometric Observations of Venus at 70-Centimeter 
Wavelength," Science 170 (1970): 1090-1092. 



146 



TO SEE THE UNSEEN 




Figure 24 

Radar interferometric image of Venus made by Don Campbell far his 1971 doctoral dissertation, which was a study of Venus 
using the Arecibo Observatory and Higuillales antennas as a radar interferometer. The resolution is about 150 km. The Alpha 
region can be seen in the lower right corner, and Beta Regio is visible in the upper left corner. (Courtesy of D. B. Campbell, 
Cornell University.) 

As Don Campbell remembered, the original antenna was owned by Sam Harris, an 
Arecibo employee, who used it for his backyard amateur radio Moon bounces. Harris was 
a self-taught engineer well known in the "ham" community for his Moon-bounce work and 
had a column in the popular ham journal QSTfor many years. "He was a real character," 
Campbell reflected. "I always enjoyed working with him and in getting this interferome- 
ter to work over the year or so that it took." 73 

The 430-MHz radar interferometer went into operation in March 1969. Jurgens, 
Campbell, and Dyce made interferometric observations of Venus between 20 March and 
27 April 1969. Unfortunately, because the interferometer antenna was so small, the radar 
sensitivity fell sharply, and they achieved a surface resolution of only 300 km. The north- 
south ambiguity had been resolved, but at the loss of resolution. From the data, nonethe- 
less, Campbell deduced that the Faraday region was the same as Goldstein's a and 



73. Campbell 7 December 1993. 



NORMAL SCIENCE 147 



Carpenter's F. He concluded, "Despite the considerable advance that the radar interfer- 
ometer represents over other methods in mapping the surface scattering of Venus at radio 
wavelengths, we still know very litde about the actual nature of the surface." 74 In other 
words, the images really said nothing about the planet's geology. 

Campbell returned to Cornell, wrote his thesis, and graduated in July 1971. He then 
returned to Arecibo as a Research Associate employed by the NAIC. An improved line 
feed promised better observations during the next Venus inferior conjunction in 1972. 
Although delays in manufacturing the new analog-to-digital converters, as well as power 
outages, caused lost observing time, Campbell mapped Venus with the radar 
interferometer and achieved a resolution of about 100 km. 'That was the last fling prior 
to the upgrade," Campbell recalled. 75 

Campbell also derived Venus topographical (relief or surface height) information 
from the 1972 data. The most notable result was the discovery of what appeared to be a 
mountainous zone located at a longitude of 100 and having a peak height of about 3 km. 
Although not at the same location as Jurgens's suspected crater, which still remained 
noted only in his dissertation, these mountains became the second clearly identified topo- 
graphical feature on the surface of Venus, following a pioneering study by Smith and 
other Lincoln Laboratory and MIT investigators at Haystack published two years earlier. 76 

Dick Goldstein also observed Venus in 1972 with a radar interferometer that com- 
bined the Mars Station with a nearby 26-meter antenna. These were Goldstein's first Venus 
observations with an interferometer. Because he did not suffer the obstacles thrown at 
Don Campbell, Goldstein was able to update his large-scale, low-resolution map of Venus, 
which now had a resolution of 10-15 km. He also assembled his first altitude map. A gray 
scale of only five levels, with each level representing a set of altitude values, indicated the 
degree of relief. The map showed a large crater about 160 km in diameter about 36 West 
longitude and 2 South latitude. Goldstein estimated the height of the crater rim to be 
about 500 meters above the crater floor. This was the first distinguishable crater Goldstein 
found in his radar data; several years earlier, though, Ray Jurgens had identified a crater 
in his Cornell dissertation. 77 

By the 1972 inferior conjunction of Venus, the combination of range-Doppler map- 
ping and radar interferometry was beginning to reveal a general overview of the planet's 
major surface features. Although Venus still looked like a strange fish bowl in radar 
images, lunar range-Doppler images looked more like photographs. These initial tentative 
steps, whatever their drawbacks, began to set in motion a shift in the planetary radar par- 
adigm from astronomy to geology. Like the far more successful (because they looked like 
and had greater resolution than ground-based photographs) lunar radar images, Venus 
radar images showed that planetary radar astronomy could tell scientists useful informa- 
tion about distant surface formations. These images were not the only techniques radar 
astronomers had for describing planetary surface conditions. Coincidental with the grad- 
ual evolution of planetary radar toward these geological problems, NASA was turning 
from Apollo to planetary missions. 



74. Campbell 7 December 1993; AIO, Research in Ionospheric Physics, Research Report RS 75 (Ithaca: 
CRSR, 31 March 1969), pp. 12-13; Ibid., Research Report RS 76 (Ithaca: CRSR, 30 September 1969), p. 23; 
Campbell, Jurgens, Dyce, Harris, and Pettengill, "Radar Interferometric Observations," pp. 1090-1092. 

75. Campbell 7 December 1993; NAIC QR Q2/1972, pp. 3-4, and Q3/1973, pp. 3-4. 

76. Campbell, Dyce, Ingalls, Pettengill, and Shapiro, "Venus: Topography Revealed by Radar Data," 
Science 175 (1972): 514-516. Smith, Ingalls, Shapiro, and Ash, "Surface-Height Variations on Venus and 
Mercury," Radio Science 5 (1970): 411-423, presented an earlier topographical study of Venus made from 
Haystack data taken over a period of years. That study was confined to the planet's equator and found a 2-km 
feature. It was remarkable for the variety of radar techniques used, as well as for its discovery of the first topo- 
graphical feature on Venus. 

77. Rumsey, Morris, R. Green, and Goldstein, "A Radar Brightness and Altitude Image of a Portion of 
Venus," Icarus 23 (1974): 1-7; Jurgens, "A Study of the Average and Anomalous Radar Scattering," pp. 87-110. 



Chapter Six 

Pioneering on Venus and Mars 

Range-Doppler mapping and radar techniques for determining the roughness, 
height variations, and other characteristics of planetary surfaces came into their own in 
the early 1970s and shaped the kinds of problems planetary radar could solve. Radar tech- 
niques and the kinds of problems they solved were cross-fertilizing forces in the evolution 
of planetary radar astronomy. In the early 1970s, NASA was shifting gears. The landing of 
an American on the Moon, the zenith of the Apollo program, was history when in 
December 1972 Apollo 17 became the last to touch down on the Moon. Now the 
unmanned exploration of the planets began in earnest. 

The usefulness of radar to planetary exploration had been argued by radar 
astronomers as early as the 1959 Endicott House conference. However, not everyone 
shared their enthusiasm. Smith and Carr, for example, in their 1964 book on radio astron- 
omy, wrote: "It is inevitable that the importance of the exploration of the planetary system 
by radar will diminish as instruments and men are carried directly to the scene by space 
vehicles. However, that time is still to come. In the meantime, the information that radar 
provides will be vital in man's great effort to conquer space." 1 Soviet radar astronomers B. 
I. Kuznetsov and I. V. Lishin expressed similar sentiments in 1967: "Certainly, radar bom- 
bardment of the planets gives less information than a direct investigation of them with 
spaceships and interplanetary automatic stations." However, they did foresee that infor- 
mation about planetary surfaces would "help designers in the development of spaceships 
intended for making a 'soft' landing on the planets." 2 

As NASA came to fund planetary radar research, experiments and NASA missions 
became linked. Goldstone antenna time depended on mission approval, while Haystack 
radar funding was tied to specific, mission-oriented tasks. It is not surprising, then, that 
planetary radar in the 1970s evolved in point and counterpoint to the NASA space pro- 
gram, at first modestly to correct data returned from Soviet and American missions to 
Venus, next to help select a Mars landing site, and then to image Venus from a spacecraft. 
This evolution followed from the precedent established by NASA's funding of lunar radar 
imaging for the Apollo program. The Pioneer Venus radar imaging and altimetry missions 
took radar astronomy off the ground and into space. Again, just as ground-based radar 
astronomy had piggybacked itself onto Big Science radio astronomy facilities, so the 
Pioneer Venus radar attached itself to a larger mission to explore the planet's atmosphere. 

The new techniques and problem-solving activities drew radar astronomers into clos- 
er contact with planetary scientists from a variety of disciplines who were not necessarily 
familiar with radar or the interpretation of radar results. It was one thing for radar 
astronomers to determine a spin rate for a planet or the value of the astronomical unit; 
astronomers easily grasped those discoveries. However, when radar astronomers described 
planetary surfaces in such abstract terms as root-mean-square slope to geologists, whose dis- 
cipline rests heavily on hands-on field knowledge, a communication problem arose and 
serious misinterpretations and misunderstandings of radar results ensued. 



1. Smith and Carr, pp. 130-131. 

2. Kuznetsov and Lishin, p. 201. 



149 



1 50 TO SEE THE UNSEEN 



The Radar Radius of Venus 

On 18 October 1967, the Soviet Venera 4 space probe entered the atmosphere of 
Venus and began to transmit data back to Earth. From that data, Soviet scientists calculat- 
ed a value for the radius of Venus, 6,079 3 km, on the assumption that the break in the 
probe's transmissions indicated that it had reached the planet's surface. On the following 
day, Mariner 5 passed within 4,100 km of Venus and conducted a series of experiments. 
From the data beamed back to Earth, Mariner scientists at JPL calculated a value for the 
radius of Venus that was compatible with that determined by their Soviet colleagues, 6,080 
10km. 

The data from Venera 4 and Mariner 5 were consistent with each other and with the 
latest optical data, which yielded a value of 6,089 6 km. However, the space and optical 
values differed markedly from the size of the radius, 6,056 1.2 km, determined by Irwin 
Shapiro, Bill Smith, and Michael Ash with the Lincoln Laboratory radars as part of the 
Planetary Ephemeris Program. 3 

If the spacecraft and optical measurements were correct, then the radar data or its 
analysis were in error. The radius of Venus was a critical radar measurement; its value, for 
example, could serve to study the planet's topography. Radar astronomers associated with 
MIT and the Haystack Observatory, Gordon Pettengill, Irwin Shapiro, Dick Ingalls, 
Michael Ash, and Marty Slade, and those at the Arecibo Observatory, Rolf Dyce, Don 
Campbell, Ray Jurgens, and Tommy Thompson, took up the challenge in collectively 
authored papers that appeared in Science and the Journal of the Atmospheric Sciences. The 
publications embraced both a general audience and atmospheric specialists. 

In addition to data collected previously at Millstone, Haystack, and Arecibo, the MLT- 
Arecibo radar astronomers added data from fresh radar observations made in 1966 and 
1967 as well as optical observations from the U.S. Naval Observatory from the period 1950 
through 1965. The magnitude of the data base was impressive and convincing. The 
Arecibo and MIT investigators analyzed their data separately and obtained radii of 6,052 
2 km and 6,048 1 km, respectively. They concluded that Mariner 5 had misjudged its 
distance from the planet's center by about 10 km, and that "the simple possibility that 
Venera 4 underestimated its altitude by about 35 km cannot yet be ruled out." 4 

Dewey Muhleman, now professor of planetary science at the California Institute of 
Technology, with Bill Melbourne and D. A. O'Handley of JPL, made observations of Venus 
between May 1964 and October 1967 with the Goldstone Mars Station. Because their data 
were reported only in internal JPL reports, Lincoln Laboratory did not use that data. 
Consequently, they asserted, their observations constituted "an entirely independent data 
source." Muhleman and his JPL colleagues determined a value for the radius of Venus of 
6,053.7 2.2 km, in strong agreement with the MIT and Arecibo results. 5 

Arvydas Kliore and Dan L. Cain, two JPL scientists on the Mariner mission, saw the 
agreement between the Caltech-JPL and the Arecibo-MIT values and realized that "the 
consistency between reductions from data taken by different radars and reduced by dif- 
ferent investigators cannot be ignored." They discovered that the different timing systems 



3. C. W. Snyder, "Mariner 5 Flight past Venus," Science 158 (1967): 1665-1669; Arvydas Kliore, Gerald 
S. Levy, Dan L. Cain, Gunnar Fjeldbo, S. Ichtiaque Rasool, "Atmosphere and Ionosphere of Venus from the 
Mariner 5 S-band Radio Occultation Experiment," Science 158 (1967): 1683-1688; Gerard H. de Vaucouleurs and 
Donald H. Menzel, "Results of the Occultation of Regulus by Venus, July 7, 1959," Nature 188 (1960): 28-33; Ash, 
Shapiro, and Smith, Astronomical Journal 72 (1967): 338-350. 

4. Ash, Campbell, Dyce, Ingalls, Jurgens, Pettengill, Shapiro, Martin A. Slade, and Thompson, The 
Case for the Radar Radius of Venus," Science 160 (1968): 985-987; Ash, Campbell, Dyce, Ingalls, Jurgens, 
Pettengill, Shapiro, Slade, Smith, and Thompson, The Case for the Radar Radius of Venus," Journal of the 
Atmospheric Sciences 25 (1968): 560-563; Shapiro 1 October 1993. 

5. William G. Melbourne, Muhleman, and D. A. O'Handley, "Radar Determination of the Radius of 
Venus," Science 160 (1968): 987-989. 



PIONEERING ON VENUS AND MARS 1 5 1 



used by the Deep Space Network to acquire Mariner 5 data, namely Station Time and 
Ephemeris Time, had introduced an error into their calculations. The amount of that 
error, 8.85 km, brought the Mariner 5 value for the radius of Venus in line with the radar 
results. 

To explain what was now the anomalous Soviet value for the radius of Venus, Kliore 
and Cain concluded that either the Venera 4 capsule landed on a peak or plateau that was 
about 25 km high and not detected by planetary radar or the capsule stopped transmit- 
ting before reaching the solid surface of Venus. The problem with Venera 4, Don 
Campbell ventured, "was tied up in an ambiguity difficulty in their own radar system, 
which was a pulsed altimeter radar. I think, frankly, that the scientists who reported the 
results did not know how it worked. It was a military radar altimeter. They were just pro- 
vided the answer, essentially. Although I don't know, and probably didn't know at the time 
either, what exactly the circumstances were, that was the impression that one got." 6 

"A Little Radar Knowledge is a Dangerous Thing." 

Well before radar astronomers began collaborating with geologists, misinterpreta- 
tions of radar data occurred. In fact, radar astronomers themselves were not immune to 
misconstruing radar results, as the case of the radar brightness of Mars illustrates. In ini- 
tial observations of that planet, radar astronomer Dick Goldstein assumed a relationship 
between radar brightness and optical darkness. Arecibo observations appeared to confirm 
that relationship, which snowballed among planetary astronomers into a hypothesis that 
correlated radar brightness and topography (continental blocks and dry ocean basins). A 
reconsideration of evidence showed no such correlation. 

When Dick Goldstein made his pioneering radar observations of Mars in 1963, he 
discovered what he thought was a relationship between radar "brightness," that is, the 
average amount of power returned in the echo from a given surface area of the planet, 
and the optical darkness of that same surface area. Goldstein constructed what he called 
a radar map of Mars, which showed variations in radar brightness. He noted, for example, 
that the Syrtis Major region appeared bright to the radar, but dark to visual observations. 
Because radar brightness is a function of surface roughness, he argued, the brightest 
radar areas were regions of flatness, while dark radar areas were topographically rough. 7 

In 1965, Goldstein observed Mars at the next opposition and again looked at the 
radar brightness of the planet's surface, this time at latitude 21 North. The average power 
returned (radar brightness) reached a maximum in the region of Trivium Charontis (an 
optically dark area) , then dropped off abruptly when the neighboring area of Elysium 
(optically bright) was the radar target. Based on the known relationship between surface 
roughness and radar brightness, Goldstein concluded the existence of a very smooth, 
strongly reflecting area extending 20 to 30 in longitude and having an unknown latitu- 
dinal extent in the region of Trivium Charontis. 8 

During the same opposition, Gordon Pettengill, Rolf Dyce, and Don Campbell 
observed Mars with the UHF radar at Arecibo. When they compared their results with an 
optical map of Mars, the Arecibo investigators found a general tendency for weak echoes 
to correlate with the (optically) lighter areas of Mars, such as Arabia, Elysium, Tharsis, and 



6. Kliore and Cain, "Mariner 5 and the Radius of Venus," Journal of Atmospheric Sciences 25 (1968): 549- 
554; Campbell 7 December 1993. Murray, pp. 90-91, provides further anecdotal accounting of Soviet embar- 
rassment over the incident. 

7. Goldstein and Gillmore, "Radar Observations of Mars," Science 141 (1963): 1172. 

8. Goldstein, "Mars: Radar Observations, "Science 150 (1965): 1715-1717. His results were reported also 
in Goldstein, "Preliminary Mars Radar Results," Radio Science 69D (1965): 1625-1627. 



1 52 TO SEE THE UNSEEN 



Amazonis, and a tendency for strong echoes to correspond with visually darker features, 
such as the regions near Trivium Charontis and Syrtis Major. They did, however, note that 
the correlation between radar brightness and optical lightness was not perfect. For 
instance, the peak radar echo near Trivium Charontis occurred at 201 longitude, which 
is on one edge of the visually dark region. Likewise, the visually darkest region of Syrtis 
Major corresponded to a local minimum in echo strength. 9 

The Arecibo results were rather convincing. Not only had they been obtained from 
roughly the same area (22 North latitude) that Goldstein had studied, but the Arecibo 
and Goldstone observations had been made at two different frequencies (UHF vs. S- 
band) . The persistence of the correlation between optical darkness and radar brightness 
at both frequencies was persuasive. 

Astronomers Carl Sagan and James B. Pollack, then at the Smithsonian Astrophysical 
Observatory, and Richard Goldstein carried out a lengthy and detailed analysis of the JPL 
1963 and 1965 radar data. They maintained and extensively documented the correlation 
between high radar reflectivity and optical darkness, despite some exceptions. Not only 
did radar bright and optically dark areas correlate; they claimed that topography and 
radar brightness also were related. Dark areas were elevations similar to continental 
blocks; bright areas were comparable to dry ocean basins. 10 The notion that Martian dark 
areas were elevated land masses rapidly gathered support from other planetary 
astronomers in the United States and Britain. 11 

Nonetheless, Pettengill, who had participated in the earlier effort at Arecibo, now 
opposed the correlation of visual darkness and radar brightness and undertook observa- 
tions at Haystack, during the 1967 opposition, specifically in order to oppose the 
prevailing hypothesis that now correlated topography and radar brightness. Pettengill 
conducted a series of straightforward, precise range measurements to establish the 
topographical variations along latitude 22 North. Then he compared those range mea- 
surements with the average planetary radius taken from the planetary ephemeris data. He 
also plotted echo power over longitude along that same latitude. 

Pettengill found no significant correlation between radar brightness and topogra- 
phy. A direct comparison between the radar results and a map of visible Martian surface 
features revealed no clear one-to-one association between bright or dark areas and 
topographical extremes. What others had observed as variations in radar brightness, 
Pettengill argued, resulted from the deviant properties of relatively small regions of the 
surface near the subradar point. Moreover, he pointed out, arguments for the hypotheti- 
cal correlation between elevation extremes and brightness had been based largely on 
conclusions drawn from a range of disparate isolated locations. Further Haystack obser- 
vations of Mars carried out under Pettengill's direction reinforced the conclusion that no 
correlation existed between regions of high radar reflectivity and optically dark areas. 12 

Perhaps one of the most notorious examples of misinterpreted radar results is that 
of Thomas Gold of Cornell University. Gold had been developing theories about the lunar 
surface since the 1950s. Long before he ever saw any radar data, Gold favored a meteoric 



9. Dyce, Pettengill, and Sanchez, "Radar Observations of Mars and Jupiter at 70 cm," The Astronomical 
Journal!?. (1967): 771-777; Campbell 7 December 1993. 

10. Carl Sagan, James B. Pollack, and Goldstein, "Radar Doppler Spectroscopy of Mars: 1. Elevation 
Differences between Bright and Dark Areas," The Astronomical Journal 72 (1967): 20-34. This article appeared 
earlier as Sagan, Pollack, and Goldstein, Radar Doppler Spectroscopy of Mars: 1. Elevation Differences between Bright and 
Dark Areas, Special Report 221 (Cambridge: SAO, 6 September 1966). 

11. See, for example, D. G. Rea, The Darkening Wave on Mars," Nature 210 (1964): 1014-1015; R. A. 
Wells, "Evidence that the Dark Areas on Mars are Elevated Mountain Ranges," Nature 207 ( 1965) : 735-736. Rea 
was at the University of California at Berkeley, and Wells at University College, London. 

12. Pettengill, Counselman, Rainville, and Shapiro, "Radar Measurements of Martian Topography," The 
Astronomical Journal 74 (1969): 461-482; Pettengill, Rogers, and Shapiro, "Martian Craters and a Scarp as Seen 
by Radar," Science 174 (1971): 1324. 



PIONEERING ON VENUS AND MARS 1 53 



explanation for lunar craters and developed an explanation for the presence of vast flat 
level surfaces that did not require the deposition of volcanic lava. His hypothesis was that 
these flat expanses consisted of dust from meteoric impacts. Gold interpreted radar obser- 
vations of the Moon as supporting the existence of a surface layer of fine rock powder sev- 
eral meters deep, which a seismic experiment carried out by Apollo 12 allegedly support- 
ed. The implications for landing an American on the Moon were obvious; an astronaut 
might sink several centimeters into the powder or even "wallow" in it. 13 

Many scientists greeted Gold's prediction of a deep layer of powder with disbelief. As 
Don E. Wilhelms wrote, 'Tour Surveyor and six Apollo landings established the strength, 
thickness, block content, impact origin, and paucity of meteoric material in the Moon's 
regolith. There is fine pulverized soil, but it is weak only for a few centimeters of its thick- 
ness. Yet Thomas Gold is still fighting the battle. Still believing radar more than geologi- 
cal sampling..." 14 Wilhelms went so far as to state, "A little radar knowledge is a dangerous 
thing." 15 Gold later defended himself by insisting that although the "Gold dust" (as it has 
come to be called) would be many meters thick, the idea of sinking in it was a "total mis- 
conception." 16 

The Apollo program started the process of bringing together radar astronomers and 
geologists. The lunar radar images created by Tommy Thompson and Stan Zisk from data 
gathered at Arecibo and Haystack contributed not inconsequentially to America's explo- 
ration of the Moon. On occasion, nonetheless, radar astronomers misinterpreted lunar 
landing sites. In one instance, a landslide was mistaken for a field of boulders at the Apollo 
17 landing site, while in another radar astronomers incorrectly characterized the rough- 
ness of the Apollo 14 Cone Crater site. These problems, however, arose not from mistak- 
en readings of radar images, but from misinterpretations of the root-mean-square slope 
and dielectric constants of the surface. 17 



Landing on Mars 



During the preparation for the Viking mission to Mars, radar astronomers encoun- 
tered the challenge of making radar data understandable to NASA mission personnel 
unfamiliar with the interpretation of radar results. Until Congress funded the Voyager 
mission to Jupiter and Saturn, Viking was NASA's biggest and most expensive program for 
planetary exploration. Viking was to land on that planet, and NASA needed a landing site 
that was both safe for the lander and interesting to scientists. Radar astronomers collect- 
ed and interpreted data to help with the selection of candidate sites. 

The selection of the Viking lander site also brought together ground-based planetary 
radar astronomy and the Stanford bistatic radar approach under the aegis of NASA. 
Ground-based planetary radar astronomy had distinguished itself from "space explo- 
ration" (the Stanford approach), but the boundary between ground-based planetary 
radar astronomy and "space exploration" softened, as radar astronomers played an 
expanding role in NASA missions of planetary exploration and as Stanford investigators 
extended their field of applications. 



13. Gold, The Lunar Surface," Monthly Notices of the Royal Astronomical Society 115 (1955): 585-604; 
Malcolm J. Campbell, Juris Ulrichs, and Gold, "Density of the Lunar Surface," Science 159 (1968): 973; Gold and 
Steven Soter, "Apollo 12 Seismic Signal: Indication of a Deep Layer of Powder," Science 169 (1970): 1071-1075; 
Gold, The Moon's Surface," in Wilmot N. Hess, Menzel and John A. O'Kcefe, eds., The Nature of the Lunar 
Surface (Baltimore: Johns Hopkins University Press, 1966), pp. 107-121; Gold, "Conjectures about the Evolution 
of the Moon," The Moon 7 (May-June 1973): 293-306. 

14. Don E. Wilhelms, To A Rocky Moon: A Geologist's History of Lunar Exploration (Tucson: The University 
of Arizona Press, 1993), p. 347. 

15. Wilhelms, p. 299. 

16. Gold 14 December 1993. 

17. Schaber 27 June 1994; Thompson 29 November 1994. 



154 TO SEE THE UNSEEN 



Images of Mars from earlier missions provided a clue in selecting candidate Viking 
landing sites. As early as 1965, Mariner 4 had flown past Mars and snapped 22 pictures of 
about one percent of the planet's surface. Mariner 6 and Mariner 7 took about 200 images 
of around 10 percent of the surface in 1969. The goal of Mariner 9, to make a complete 
photographic map of Mars was thwarted; when the spacecraft arrived at its destination, a 
planet-wide dust storm concealed most of the surface. Once the storm appeared to sub- 
side, Mariner 9 began to transmit images to Earth in early 1972, and the study of Martian 
topography began in earnest. 18 

Unlike the Mariner flybys, Viking was to study Mars by landing on its surface. A pair 
of orbiters was to focus on atmospheric studies, while a pair of landers studied the surface, 
if all went well. If the Viking landers were to touch down on a large rock or precariously 
on an edge, the entire mission might be lost. The clearance under the lander body was 
only 23 cm (nine inches) , so a relatively smooth landing surface was a prime mission req- 
uisite. 

NASA selected landing and backup sites for two landers. The sites had to be around 
25 North latitude; at any other latitude, the orbiter solar panels would not receive suffi- 
cient solar energy to keep the spacecraft's batteries charged. That power was critical to the 
transmission of telemetry to Earth. 

A major criteria for selecting candidate landing sites was the potential availability of 
water. Water meant the possibility of finding life, which was a major mission objective. 
Chryse, located at 19.5 North and 34 West, was scientifically interesting, because it is 
located at the lower end of a valley where the largest group of Martian channels diverges. 
The site may have been a drainage basin for a large portion of equatorial Mars and, there- 
fore, would have collected deposits of a variety of surface materials. 19 

Despite the scientific interest in Chryse as the prime Viking landing site, the high- 
resolution Mariner 9 images lacked sufficient resolution to determine the site's safety. As 
Don Campbell recalled: "NASA was very concerned about how rough the surface was at 
the landing site. None of the Mariner 9 imagery had any hope of giving information at 
scales of 10 cm to a meter, which was the amount of surface roughness that they cared 
about." 20 Mariner 9 images had a resolution of about 100 meters, roughly the size of a 
football field, and simply did not show objects small enough to jeopardize the touchdown 
of the lander, which had a clearance of only 23 cm. The radar data, in contrast, were capa- 
ble of indicating surface roughness down to objects only a few centimeters across. Once 
again, radar was going to try to solve a problem left unresolved by optical methods. 

The Stanford Center for Radar Astronomy 

In order to help select candidate Viking landing sites, NASA turned to radar astron- 
omy and its ability to appraise gross and fine surface characteristics. The chief advocate 
for the use of radar data was Carl Sagan. Sagan was concerned about the possibility that 
the first lander might disappear in quicksand at one of the equatorial sites. In general, he 
believed that too much stress had been placed on visual images with a resolution of only 
100 meters and not enough on radar, which could indicate surface irregularities at the 



18. Corliss, The Viking Mission to Mars, NASA SP-334 (Washington: NASA, 1974), pp. 6-8; Thomas A. 
Mutch, Raymond E. Arvidson, James W. Head, III, Kenneth L.Jones, R. Stephen Saunders, The Geology of Mars 
(Princeton: Princeton University Press, 1976). 

19. Martin Marietta Aerospace, The Viking Mission to Mars (Denver: Martin Marietta, 1975) , pp. 111-21 to 
IH-23; Edward Clinton Ezell and Linda Neuman Ezell, On Mars: Exploration of the Red Planet, 1958-1978, NASA 
SP-4212 (Washington: NASA, 1984), p. 298. 

20. Campbell 8 December 1993. 



PIONEERING ON VENUS AND MARS 155 



10-cm scale. Sagan urged further study of the meaning of the radar data, so that the prop- 
erties of the Martian soil could be better evaluated. 

In response to Sagan's urging, on 1 March 1973, Tom Young and Gerald Soffen, 
Viking science integration manager and project scientist, respectively, met with Von 
Eshleman and Len Tyler of the Stanford Center for Radar Astronomy. Both already were 
investigators on Viking with a radio scattering experiment. Young and Soffen asked Tyler 
to acquire, analyze, and interpret radar data and to set up a radar study team for the selec- 
tion of Viking landing sites. Tyler agreed. 21 

The Viking Project Office probably approached the Stanford Center for Radar 
Astronomy because Eshleman and Tyler already were Viking investigators, but also 
because of the Center's experience in interpreting Doppler spectra from the lunar sur- 
face. The Stanford Center for Radar Astronomy (SCRA) was a joint venture of Stanford 
University and the Stanford Research Institute (SRI) created in 1962 to foster scientific 
and engineering efforts and to provide graduate student training in radar astronomy and 
space science. It was the umbrella organization for Eshleman and his program of bistatic 
radar astronomy. A NASA grant underwrote the Center itself, while additional military 
and civilian awards supported a range of theoretical and experimental radio and radar 
research on space, ionospheric, and communication theory topics. 22 

Len Tyler, as did his Stanford colleague Dick Simpson, brought considerable knowl- 
edge of radar techniques to the effort. A graduate of Georgia Institute of Technology, 
Tyler had been at the SCRA since 1967, when he received his doctorate in electrical engi- 
neering from Stanford under Von Eshleman. Tyler invited Dick Simpson to work on the 
Viking data. Simpson, a graduate of the MIT electrical engineering program, had joined 
the SCRA in 1967 as a research assistant while working on his MS and Ph.D. in electrical 
engineering. 23 

Later, during the 1978 Mars opposition, Simpson and Tyler conducted 29 bistatic 
radar observations using the Viking 1 and 2 orbiter spacecraft in conjunction with the 
DSN antennas at Goldstone and Tidbinbilla (near Canberra, Australia) to study Mars sur- 
face roughness and scattering properties, and Simpson made ground-based monostatic 
radar observations of Mars, not associated with the Viking project, at Arecibo. 24 Their 
radar work, however, began much earlier, during the Apollo era. 

For his doctoral thesis, Tyler had developed a method for creating two-dimensional 
surface images of the Moon using an Earth-based transmitter and a spacecraft receiver 
and based on theoretical work laid out earlier by another SCRA investigator, Gunnar 
Fjeldbo (now known as Lindal). 25 Tyler first applied his bistatic imaging method on 
Explorers 33 (which missed the Moon) and 35, the first U.S. spacecraft to orbit the Moon, 



21. Tyler 10 May 1994; Ezell and Ezell, pp. 309 and 320-321; "VOIR, Proposal to the NASA Management 
Section, 2/79," Box 13, JPLMM. 

22. SCRA, Research at the Stanford Center for Radar Astronomy, semi-annual status report no. 2 for the peri- 
od 1 July-31 December 1963 (Stanford: RLSEL, February 1964), pp. 3-4; Ibid., no. 4 for the period 1 July - 
31 December 1964 (Stanford: RLSEL, January 1965), pp. 2-3; Ibid., no. 5 for the period 1 January-30June 1965 
(Stanford: RLSEL, July 1965), pp. 5-6; Ibid., no. 6 for the period 1 July-31 December 1965 (Stanford: RLSEL, 

January 1966), p. 4; Ibid., no. 7 for the period 1 January-31 June 1966 (Stanford: RLSEL, August 1966), p. 5; 
Ibid., no. 9 for the period 1 January-30 June 1967 (Stanford: RLSEL, 9 July 1967), pp. 6-8; John E. Ohlson, 
A Radar Investigation of the Solar Corona, SU-SEL-67- 071, Scientific Report 21 (Stanford: RLSEL, August 1967). 

23. Simpson 10 May 1994. 

24. Richard A. Simpson and G. Leonard Tyler, "Viking Bistatic Radar Experiment: Summary of First- 
Order Results Emphasizing North Polar Data," Icarus 46 (1981): 361-389; Simpson and Tyler, "Radar 
Measurement of Heterogeneous Small-Scale surface Texture on Mars: Chryse,"/ouma/ of Geophysical Research 85 
(1980): 6610-6614; Simpson 10 May 1994. 

25. Fjeldbo, "Bistatic-Radar Methods for Studying Planetary Ionospheres and Surfaces," Ph.D. diss., 
Stanford University, 1964, especially pp. 64-82. Later published as Fjeldbo, Bistatic-Radar Methods for Studying 
Planetary Ionospheres and Surfaces, SR 2 (Stanford: RLSEL, 1964). 



1 56 TO SEE THE UNSEEN 



and obtained crude meter-scale measurements of surface roughness and radar bright- 
ness. 26 With Simpson, Tyler performed bistatic radar experiments on the Moon using the 
Apollo 14, 15 (at 13 and 116 cm), and 16 (at 13 cm only) command service modules while 
those vehicles were in lunar orbit; at the same time, they were receiving the S-band (13 
cm) signals at Goldstone and the VHF (116 cm) signals at the Stanford 46-meter (150-ft) 
dish. However, Tyler and Simpson did not do imaging; they were more concerned with 
scattering mechanisms. 27 

Mars Radar 

Tyler and Simpson began working on the Viking landing site selection problem by 
surveying and re-analyzing the available data. Radar data from several oppositions already 
were available, and those data obtained during the 1965 opposition were from the latitude 
of the preferred Viking landing sites, around 20 North. Radar studies of Mars made dur- 
ing the 1969 opposition provided useful topographical and surface roughness measure- 
ments, though not at latitudes interesting to the Viking mission. Haystack observed a 
swath of the planet's surface near the equator (latitudes 3 and 12 North), while 
Goldstone took observations at three latitudes (3, 11, and 12 North). 28 



26. Tyler 10 May 1994; Tyler, The Bistatic Continuous-Wave Radar Method for the Study of Planetary Surfaces, 
SU-SELr65-096, Scientific Report 13 (Stanford: RLSEL, October 1965), which later appeared as Tyler, The 
Bistatic, Continuous-Wave Radar Method for the Study of Planetary Surfaces, "Journal of Geophysical Research 71 
(1966): 1559-1567; Tyler, Bistatic-Radar Imaging and Measurement Techniques for the Study of Planetary Surfaces, SU- 
SEL-67-042, Scientific Report 19 (Stanford: RLSEL, May 1967); Tyler and Simpson, Bistatic-Radar Studies of the 
Moon with Explorer 35: Final Report Part 2, SR 3610-2, SU-SEL-70-068 (Stanford: RLSEL, October 1970) ; Tyler and 
Simpson, "Bistatic Radar Measurements of Topographic Variations in Lunar Surface Slopes with Explorer 35," 
Radio Science 5 (1970): 263-271; SCRA, Proposal to the National Aeronautics and Space Administration for Bistatic Radar 
Astronomy Studies of the Surface and Ionosphere of the Moon based upon Transmission from the Earth and Reception in a 
Surveyor Orbiter, Proposal RL 21-62 (Stanford: RLSEL, 7 September 1962), Eshleman materials. 

27. Tyler 10 May 1994; Simpson 10 May 1994; Simpson and Tyler, "Radar Scattering Laws for the Lunar 
Surface," IEEE Transactions on Antennas and Propagation AP-30 (1982): 438-449; Simpson, "Lunar Radar Echoes: 
An Interpretation Emphasizing Characteristics of the Leading Edge," Ph.D. diss., Stanford University, 1973. 

28. Tyler 10 May 1994; Rogers, Ash, Counselman, Shapiro, and Pettengill, "Radar Measurements of 
Surface Topography and Roughness of Mars," Radio Science 5 (1970): 465-473; Goldstein, Melbourne, Morris, 
George S. Downs, and O'Handley, "Preliminary Radar Results of Mars," Radio Science 5 (1970): 475-478. 



PIONEERING ON VENUS AND MARS 



157 




Figure 25 

Outline of Mars topography at 8 north of the equator released byJPL in July 1969. The outer white circle indicates a six-mile- 
high scale. The inner irregular line traces topographical variations found by radar. Syrtis Major and Trivium Charontis were 
found to be. long slopes. The correlation of radar topographic data with known features in Mars photographic images aided 
geologists ' ability to interpret the physical and historical geology of the planet. (Courtesy of Jet Propulsion Laboratory, photo 
no. 331-4539.) 

The 1969 and earlier data, moreover, were too noisy to be of any use in sorting out 
a Viking landing site. The best data had been collected during the 1971 opposition, when 
Mars came closer to Earth than it would again for 17 years. Goldstone achieved its high- 
est resolutions to date; results showed a rugged terrain, with elevation differences greater 
than 13 km from peak to valley. Altitude profiles showed heavy cratering, including 
several large craters 50 to 100 km in diameter and 1 to 2 km deep. Haystack also made 
high-resolution Mars radar observations during the 1971 opposition, measured surface 
heights with relative errors down to about 75 meters, and correlated craters detected by 
radar with those in images taken by Mariner. 29 



29. Goldstein 14 September 1993; Downs, Goldstein, R. Green, Morris, "Mars Radar Observations, A 
Preliminary Report," Science 174 (1971): 1324-1327; Downs, Goldstein, R. Green, Morris, and Reichley, "Martian 
Topography and Surface Properties as Seen by Radar: The 1971 Opposition," Icarus 18 (1973): 8-21; Pettengill, 
Shapiro, and Rogers, Topography and Radar Scattering Properties of Mars," Icarus 18 (1973): 22-28; Pettengill, 
Rogers, and Shapiro, "Martian Craters and a Scarp as Seen by Radar," Science 174 (1971): 1321-1324. 



1 58 TO SEE THE UNSEEN 



Nonetheless, even that high-resolution data was not useful to the selection of a 
Viking landing site. Because of the geometries of the Earth and Mars during that opposi- 
tion, planetary radar astronomers observed the southern hemisphere of the planet. The 
Goldstone radar observed Mars at latitude 16 South. Haystack observations during the 
1971 opposition also examined southern latitudes. 30 The best candidates for the Viking 
mission were in the northern hemisphere. 

Thus, in 1973, when Tyler undertook the interpretation of Mars radar data for the 
selection of the Viking landing sites, radars had not observed the preferred Viking land- 
ing area near 20 North since 1967, nor any of the backup sites near the equator prior to 
1975. The Viking Project Office funded a round of Mars radar observations in 1973 at the 
Haystack, Arecibo, and Goldstone radar telescopes at UHF, S-band, and X-band frequen- 
cies. Don Campbell and Rolf Dyce provided the Arecibo data, while Dick Goldstein and 
George Downs took the Goldstone data, and Gordon Pettengill furnished the Haystack 
data. 31 

The 1973 Haystack Mars data was placed in the same format as that obtained at 
Arecibo in order to facilitate their comparison. Although Haystack provided an abun- 
dance of radar data, its signal-to-noise ratio was generally too low for a detailed study of 
surface characteristics. The Haystack klystron was acting up, 32 and Haystack ceased to par- 
ticipate in the Viking mission; shortly thereafter Haystack stopped all planetary radar 
experiments. 

The 1973 Viking Mars data provided no direct information on potential landing 
sites. The orbital geometries of Earth and Mars meant that the subradar points of the 
three telescopes swept areas in the southern hemisphere, between latitudes 14 and 22 
South far from either the main or backup landing sites. 33 The 1973 data, nonetheless, pro- 
vided an opportunity to better understand the radar properties of the Martian surface and 
for Tyler, in particular, to begin the difficult task of explaining the surface roughness of 
Mars in terms of root-mean-square (rms) slope to an audience unacquainted with the 
interpretation of radar data. 

Radar Tutorials 

Mariner images made the surface of Mars obvious to everyone. Radar data on sur- 
face roughness was not at all obvious and required expert interpretation. The "rift 
between believers in radar and believers in photography," in the words of Edward Clinton 
Ezell and Linda Neuman Ezell, first appeared at a meeting of the Viking landing site work- 
ing group on 25 April 1972, 34 well before Tyler and radar became a part of the site selec- 
tion process. 



30. Pettengill, Shapiro, and Rogers, "Topography and Radar Scattering Properties of Mars," Icarus 18 
(1973): 22-28; Pettengill, Rogers, and Shapiro, "Martian Craters and a Scarp," pp. 1321-1324. 

31. Simpson, Tyler, and Belinda]. Lipa, Analysis of Radar Data from Mars, SR 3276-1, SU-SEL-74-047 
(Stanford: SCRA, October 1974). 

32. Ingalls 5 May 1994; Simpson 10 May 1994. 

33. Memorandum, Sebring to Distribution, 9 December 1970, 44/2/AC 135; "Applications of High 
Power Radar to Studies of the Planets, NASA, 7/1/69- 6/30/70," 67/2/AC 135; "Radar Studies of the Planets, 
NASA, 7/1/72-6/30/73," 68/2/AC 135, MITA; NEROC, Final Progress Report Radar Studies of the Planets, 29 August 
1974, pp. 1-2; NEROC, Semiannual Report of the Haystack Observatory, 15 July 1972, p. ii; Simpson, Tyler, and Lipa, 
"Mars Surface Properties Observed by Earth-Based Radar at 70-, 12.5-, and 3.8-cm Wavelengths," Icarus 32 
(1977): 148. For the radar results themselves, see Pettengill, John F. Chandler, Campbell, Dyce, and D. M. 
Wallace, "Martian Surface Properties from Recent Radar Observations," Bulletin of the American Astronomical 
Society 6 (1974): 372; Downs, Goldstein, R. Green, Morris, and Reichley, "Martian Topography and Surface 
Properties as Seen by Radar: The 1973 Opposition," Icarus 18 (1973): 8-21; Downs, Reichley, and R. Green, 
"Radar Measurements of Martian Topography and Surface Properties: The 1971 and 1973 Oppositions," Icarus 
26 (1975): 273-312. 

34. Ezell and Ezell, p. 298. 



PIONEERING ON VENUS AND MARS 159 



The key radar information on surface characteristics was not expressed visually, but 
mathematically. The abstract results were neither visual nor directly accessible by any of 
the senses. Moreover, the transformation of raw radar data into information on surface 
characteristics involved the interpretation of the data in terms of scattering laws and their 
expression as degrees of rms slope. The number of degrees of rms slope indirectly but reli- 
ably described the planet's surface roughness. 

When a radar wave strikes an irregular planetary surface covered by boulders or 
other material with multiple sides, a complex scattering process takes place. Some power 
returns to the radar, some power is deflected away from the radar return path, while some 
power scatters among the boulders. The rougher the surface, the less power returns to the 
radar and the flatter is the return power spectra. 

Because each radar target has a different surface makeup, its scattering behavior 
varies. Radar astronomers have sought general laws that describe scattering behavior. 
These scattering laws are mathematical descriptions of how much power is reflected back 
towards the radar at different angles of incidence. They are important tools for interpret- 
ing planetary radar data. At Haystack and Arecibo, radar investigators used what had 
become known as the "Hagfors Law," named after the Cornell University ionosphericist 
and radar astronomer. 

The Hagfors Law mathematically expresses the general roughness of a planetary or 
lunar surface in terms of average slope. The root-mean-square is a specific type of math- 
ematical average for the expression of these average slopes. When using the Hagfors Law, 
the value for the slope varies up to 3, the upper theoretical limit for the validity of the 
assumptions underlying the Hagfors Law, although in practice much higher slope values 
are normal. The 1973 slope estimates for Mars ranged from 0.5 to at least 3, suggesting 
that some areas, those closest to 0.5, were suitable for a Viking landing. However, none 
of the 1973 radar experiments had observed areas of potential Viking landing sites. 35 

Tyler and the members of his radar study group presented their results to the land- 
ing site working group meeting at Langley on 4 November 1974. Tyler announced that his 
study group had learned a great deal: overall, the Martian surface was very heterogeneous; 
Mars tended to have greater variation in surface reflectivity than Earth or the Moon; and 
the planet appeared smoother than the Moon to the radar. However, he concluded, data 
acquired in the southern hemisphere could not be applied to northern latitudes without 
variation. Also, correlation between radar features and Mariner 9 imagery was poor. 

Both Tyler and Gordon Pettengill "laced their presentations strongly with tutorial 
material which greatly enhanced the ability of the group to understand and correctly 
interpret their findings," reported Edward and Linda Ezell. 36 After all, geologists would 
rather think about rocks than about Hagfors' Law, rms slopes, or dielectric constants, and 
those in charge of making the landing site selection had no knowledge of radar. 37 The 
abstract nature of the radar data, as well as its complex and difficult interpretation, had 
an impact on the actual use of radar in the selection of the Viking landing site. 



35. Simpson, Tyler, and Lipa, "Mars Surface Properties Observed by Earth-Based Radar at 70-, 12.5-, and 
3.8-cm Wavelengths," /cams 32 (1977): 156. 

36. Ezell and Ezell, p. 322. 

37. Simpson 10 May 1994; Schaber 27 June 1994; Shoemaker 30 June 1994; Soderblom 26 June 1994; 
Gold 14 December 1993. 



160 



TO SEE THE UNSEEN 




Figure 26 

The radar data used to help select candidate landing sites for Viking often were expressed in degrees ofrms slope. This illus- 
tration depicts the abstract nature of that radar data. Above, (e) is the rms slope derived from the roughness data obtained near 
latitude -16 and shown in (b). (a) through (c) were obtained by fitting the Hagfors scattering law to measured angular power 
spectra, while (d) was surface reflectivity derived from data in (a) and (b). (Courtesy of Jet Propulsion Laboratory.) 



The Landing Site 



The selection of the final landing site of Viking 1 was a long, tedious, and dramatic 
process. 38 The sites under consideration at the last minute, literally during the two weeks 
that Viking orbited Mars, all had been either observed by radar or photographed. Part of 
the problem was the lack of overlap between the radar and optical data. Areas with good 
radar data had poor photographic documentation, while sites with good photographic 
views had poor radar data. Everybody wanted a safe landing; nobody wanted to take a 
chance with a site confirmed by only radar or only photographs. The indecision foiled an 
earlier interest in landing Viking on the Fourth of July in honor of the country's bicen- 
tennial. 

In order to acquire additional information on the candidate landing sites, the Viking 
Project Office commissioned another round of radar observations by Goldstone and 
Arecibo. Observing conditions were not ideal, because Earth and Mars were not in oppo- 
sition. However, the Arecibo S-band (2380 MHz; 13 cm) 400-kilowatt radar had just come 
on line, and Tyler recommended making additional Arecibo observations with it. Earlier 
Mars radar studies had been conducted only when Mars-Earth distances were less than 
one astronomical unit. Signal strengths during the August 1975-February 1976 equatori- 
al observations were good, but the Earth-Mars distance reached 2 astronomical units in 
May : July 1976.39 



38. For a full discussion, see Ezell and Ezell, pp. 317-346, as well as Downs 4 October 1994. 

39. Simpson, Tyler, and Lipa, Analysis of Radar Data from Mars; Simpson, Tyler, and Campbell, "Arecibo 
Radar Observations of Mars Surface Characteristics in the Northern Hemisphere," Icarus 36 (1978): 156-157. 



PIONEERING ON VENUS AND MARS 161 



Arecibo observed Mars between August 1975 and July 1976 over the latitudes 
between 12 South and 24 North. The results between 12 South and 4 North were rel- 
evant to potential alternate (i.e., backup) Viking sites. Between October 1975 and April 
1976, Goldstone observed the two regions Syrtis Major and Sinus Meridiani, particularly 
a number of proposed Viking landing sites, including the prime site (called Al) near lon- 
gitude 34 and latitude 19.5 North. As a result of the radar data, the Al site was rejected 
on 26 June 1976, while other sites came under consideration. 40 

Simpson, Tyler, and Campbell made additional Arecibo observations for the Viking 
Project Office near 20 North latitude, the latitude of the landing site, particularly the 
Viking Chryse and Tritonis Lacus (the A2 site, first alternate to Al) landing areas. The 
search for a suitable site then moved toward the northwest where a region designated 
A1NW was tentatively selected because of its apparent smoothness as seen from orbit. The 
A1NW site was finally abandoned because of its questionable radar properties. It was 
toward the west that the Viking site selection and certification teams moved after turning 
down A1NW. 41 



Did Radar Help? 



Had radar observations and expressions of rms slope actually helped in the selection 
of the final Viking 1 landing site? Certainly, Tyler's reports to the landing site working 
group did not go totally unheeded, and radar turned down some potential but suspect 
landing sites. As NASA official John E. Naugle wrote in November 1976, 'The choice of 
the actual landing site was eventually based on a combination of the S-band [Arecibo] 
radar data and high resolution photography obtained from the Viking 1 Orbiter." 42 
However, not everyone was as diplomatic as Naugle; some doubted the utility of the radar 
data. 

Tom Young, Viking science integration manager, believed that radar data eventually 
played a role, although when the project selected initial landing site candidates, he admit- 
ted that, "radar played no role, because we weren't smart enough to know how to use it." 
On the other hand, James Martin, Viking Project Manager, remained skeptical about the 
utility of the radar data. Radar provided no useful information, he felt, although it was "an 
input and a source of information that [we] could not ignore." Frankly, he admitted, 'The 
fact that it [radar] was so different scared me off." 43 

It was that difference, the general unfamiliarity with radar data, that raised a barrier 
to the use of radar results. "People didn't quite know what to make of us," Tyler explained. 
"People were willing to listen, but it was clear that they didn't like the answer!" Farther to 
the cynical side was the judgement of Dick Simpson: "I've always said that the radar con- 
tribution to picking landing sites on Mars probably came out with a net result of zero.. ..If 
we'd never been involved, they probably would have had the same end result, but we got 
to play in the game and sometimes that's part of it." George Downs, who analyzed the 
Mars radar data at JPL, was convinced that project personnel simply looked for a site as 
Viking 1 orbited Mars, ignoring the radar data entirely. The attitude of many, he felt, was 
that the radar astronomers were getting their answers as if from a ouija board. 44 



40. Simpson, Tyler, and Campbell, "Arecibo Radar Observations of Martian Surface Characteristics 
Near the Equator," Icarus 33 (1978): 102-115; Downs, R. Green, and Reichley, "Radar Studies of the Martian 
Surface at Centimeter Wavelengths: The 1975 Opposition," Icarus 33 (1978): 441-453. 

41. Simpson, Tyler, and Campbell, "Mars Surface Characteristics in the Northern Hemisphere," 
pp. 153-173. 

42. John E. Naugle to H. Guyford Stever, 8 November 1976, NHOB. 

43. Ezell and Ezell, p. 357. 

44. Tyler 10 May 1994; Simpson 10 May 1994; Downs 4 October 1994. 



1 62 TO SEE THE UNSEEN 



The radar data presented was indeed quite different; it was degrees of rms slope, 
rather than images universally understood. Perhaps if range-Doppler mapping of Mars 
had been possible, the difference would not have been so great. Still, the episode illus- 
trated the kinds of challenges that radar astronomers would have to confront as they 
played an increasing role in planetary exploration and sought to share their results with 
scientists who lacked an understanding of radar. It was simply not enough to meet with 
planetary geologists and other scientists; radar astronomers had to communicate their 
results in a way understandable by other scientists. 

The availability of the Mars radar data at JPL was the catalyst for the kind of inter- 
disciplinary communication and collaboration that interpreting the radar results 
demanded. George Downs struck up an alliance with Ladislav Roth at JPL and Gerald 
Schubert at UCLA. Roth and Schubert saw value in the radar data; that is, the topo- 
graphical information, not the surface roughness measurements. Roth, in fact, had 
approached Downs to collaborate in interpreting the radar topographical data, and sev- 
eral studies grew out of that collaboration. 45 



A Venus Radar Mapper? 



Concurrently with Viking preparations, NASA planned a mission to Venus. Pioneer 
Venus marked a significant departure for radar astronomy. Don Campbell and Tor 
Hagfors had distinguished planetary radar astronomy from space exploration, in particu- 
lar, the bistatic radar work done at Stanford University. Pioneer Venus challenged that dis- 
tinction; it was no longer ground-based planetary radar astronomy, and it marked a sig- 
nificant entree into a new area of Big Science. 

Instead of Big Science providing a large, Earth-based dish, like the Arecibo radar, 
spacecraft missions furnished the opportunity, but not the hardware, to do planetary 
radar astronomy from a point just above the target, not millions of kilometers away. Like 
piggybacking radar astronomy onto an Earth-based facility, placing a radar experiment 
and its necessary hardware on a spacecraft demanded participating in the politics of Big 
Science. Radar astronomy aboard Pioneer Venus remained Little Science, though, con- 
ducted by a single investigator, Gordon Pettengill, who carried out the entrepreneurial 
burden of placing the radar instrument on the spacecraft and who brought fellow ground- 
based radar astronomers into the project as analyzers of the radar data. 

Pioneer Venus also facilitated the shift of planetary radar toward serving the plane- 
tary geology community. Within the working groups established by NASA space missions, 
planetary radar astronomers and planetary geologists worked together. Behind this shift, 
too, was the ability of radar astronomers to solve problems of interest to geologists. If plan- 
etary radar astronomy had focused solely on refining planetary orbital parameters, the 
prime users of planetary radar results would have remained astronomers. Radar 
techniques that described planetary surfaces, in contrast, solved problems of interest to 
geologists, especially those geologists at the United States Geological Survey (USGS) inter- 
ested in planetary geology, or what the USGS called astrogeology. The shift to geology was 
an educational experience for both geologists and radar investigators, and it eventually 
manifested itself in the journals and professional societies attended by planetary radar 
astronomers and culminated in the Magellan mission to Venus. 

The idea of using radar to image Venus from a probe predated the Pioneer Venus 
project. The official history of Pioneer Venus dates the beginning of the project to 



45. Downs 4 October 1994; Ladislav E. Roth, Downs, Saunders, and Gerald Schubert, "Radar Altimetry 
of South Tharsis, Mars," Icarus 42 (1980): 287-316; Roth, Saunders, Downs, and Schubert, "Radar Altimetry of 
Large Martian Craters," Icarus 79 (1989): 289-310. 



PIONEERING ON VENUS AND MARS 1 63 



October 1967, shortly after the Venera 4 and Mariner 5 spacecraft visited Venus. Three 
scientists, Richard M. Goody (Harvard University), Donald M. Hun ten (University of 
Arizona; Kitt Peak National Observatory), and Nelson W. Spencer (Goddard Space Flight 
Center) formed a group to consider the feasibility of exploring the Cytherean atmosphere 
from a spacecraft. The group's formation led to a study published in January 1969 by the 
Goddard Space Flight Center. 46 

The idea of mapping Venus with a radar started much earlier. As early as 1959, NASA 
contracted with the University of Michigan to design a Venus radar. In 1961 , NASA let out 
three more grants and contracts to develop radars for a future Venus mission to map the 
planet's surface to investigators at the University of New Mexico, MIT, and Ohio State. 47 
In 1961, for example, NASA funded a study under J. F. Reintjes, Director of MIT's 
Electronics Systems Laboratory, "to perform an investigation of radar techniques and 
devices suitable for the exploration of the planet Venus." NASA awarded the funds 
because the space agency saw radar as an attractive technique for exploring the surface of 
Venus and as "a logical experiment for a Venus flyby or orbiter." 

Developing a radar system appropriate for space travel presented numerous prob- 
lems. The equipment had to meet certain weight, space, and reliability criteria. The MIT 
goal was to design and build a space radar that required fewer than 100 watts and weighed 
no more than 50 pounds. After completion of an engineering model by Reintjes and the 
MIT Electronics Systems Laboratory, in October 1967, tests aboard an aircraft, the 
Convair CV-990 owned by NASA Ames Research Center, began. 48 

Throughout the 1960s, then, and well before the formation of the Goddard study 
group in 1967, the idea of imaging Venus with a spacecraft-borne radar was already "in the 
air." But before a spacecraft could carry a radar to Venus, NASA had to formulate and 
fund a voyage of exploration to the planet. In June 1968, a Space Science Board study on 
planetary exploration urged NASA to send a space probe to Venus, though without rec- 
ommending inclusion of a radar experiment. 49 By June 1970, the NASA program of plan- 
etary exploration still contained no significant Venus missions. The planned flyby of Venus 
and Mercury was essentially a Mercury mission with only a small contribution to Venus 
science. In contrast, NASA had a robust plan for exploring Mars and an ambitious 
program for investigating the outer planets. 50 

In June 1970, to address the lack of a serious Venus mission, the NASA Lunar and 
Planetary Missions Board and the Space Science Board brought together 21 scientists to 
study the scientific potential of a mission to Venus (Table 3). Richard Goody and Donald 
M. Hunten, who had helped start the Goddard study, co-chaired the meeting. Their 
report, known as the Purple Book because of the color of its cover, recommended that 
exploration of Venus should be prominent in the NASA program for the 1970s and 1980s. 
The group presented its recommendations to NASA management, and the Space Science 
Board endorsed them. 51 

Significantly, the Purple Book study brought together a planetary radar astronomer, 
Gordon Pettengill, then Director of the Arecibo Ionospheric Observatory, and a planetary 
geologist, Harold Masursky of the USGS. Pettengill's participation in the Purple Book 



46. Richard O. Fimmel, Lawrence Colin, and Eric Burgess, Pioneer Venus, NASA SP-461 (Washington: 
NASA, 1983), pp. 14-15; Colin, The Pioneer Venus Program, " Journal of Geophysical Research 85 (1980): 7575. 

47. Tatarewicz, pp. 150-151. 

48. Memorandum, Oran W. Nicks, 10 March 1966, and Memorandum, Brunk, 29 November 1966, 
NHOB; J. F. Reintjes and J. R. Sandison, Venus Radar Systems Investigations Final Report (Cambridge: MIT, 
Electronic Systems Laboratory, Department of Electrical Engineering, March 1970), Pettengill materials. 

49. Space Science Board, Planetary Exploration, 1968-1975 (Washington: National Academy of Sciences, 
1968). 

50. Space Science Board, Venus: Strategy for Exploration (Washington: National Academy of Sciences, June 
1970), p. 3. 

51. C. H. Townes, Preface, Space Science Board, Venus: Strategy for Exploration, n.p. 



164 



TO SEE THE UNSEEN 



Table 3 


Purple Book Scientists 




Scientist 


Institution 






Richard M. Goody, Chair 


Harvard University 






Donald M. Hunten 


Kitt Peak National Observatory 






Don L. Anderson 


California Institute of Technology 






W. Ian Axford 


University of California, San Diego 






Alan H. Barrett 
Leverett Davis, Jr. 


Massachusetts Institute of Technology 
California Institute of Technology 






Thomas M. Donahue 
John C. Gille 


University of Pittsburgh 
Florida State University 






Seymour Hess 


Florida State University 






Garry E. Hunt 


Atlas Computer Laboratory 






Robert G. Knollenberg 


University of Chicago 






John S. Lewis 


Massachusetts Institute of Technology 






Michael B. McElroy 


Kitt Peak National Observatory 






Gordon H. Pettengill 


Arecibo Ionospheric Observatory 






Robert A. Phinney 


Princeton University 






S. Keith Runcorn 


University of Newcastle 






Verner E. Suomi 


University of Wisconsin 






Patrick Thaddeus 


Columbia University 






G. Leonard Tyler 


Stanford University 






James A. Weiman 


University of Wisconsin 






George W. Wetherill 


University of California, Los Angeles 







study marked his initial involvement in Pioneer Venus. 52 By then, Pettengill, the future 
Professor of Planetary Physics in the MIT Earth and Planetary Sciences Department, had 
acquired stature in his field, having been one of the radar astronomy pioneers at Lincoln 
Laboratory, but also as Associate Director, then as Director, of the prestigious Arecibo 
Observatory. 

Masursky had joined the USGS after graduating from Yale in 1947. After a number 
of years as a general geologist, Masursky joined the USGS's Branch of Astrogeologic 
Studies. In 1967, he became chief of the astrogeology branch, then starting in 1971 and 
until his death, chief scientist of that branch. Masursky was a science investigator on 
almost every NASA flight project to the Moon and the planets, including the Ranger, 
Lunar Orbiter, Surveyor, Apollo, Mariner 9, and Viking missions. 53 

The Purple Book meeting thus was a first step in planetary radar's shift toward geol- 
ogy, providing an initial setting for planetary radar and geology to interact and to devel- 
op a common approach for the study of Venus's surface, within the broader context of 
NASA-sponsored research of the planet's atmosphere. As the Purple Book itself noted, the 
space missions of the 1960s had given rise to new fields of study: "Very rapidly studies of 
planetary meteorology, planetary aeronomy, planetology, and planetary biology emerged 
which involved, in the main, research workers from the parallel terrestrial disciplines. 
Earth and planetary studies suddenly merged and simultaneously diverged from astrono- 
my. In some major universities, departmental and research center organization was 
changed to meet this development." 54 

Images sent back from space had encouraged geologists, like Hal Masursky, to 
become interested in planetary surfaces and in the processes that shaped them. However, 
ground-based radar images of Venus had yet to find their audience among planetary geol- 
ogists. 55 



52. Pettengill 28 September 1993. 

53. V-Gram no. 12 (July 1987): 15; "Harold Masursky," in R. R. Bowker, comp., American Men and Women 
of Science, 18th edition (New Providence, NJ: R. R. Bowker, 1992), vol. 5, p. 275. 

54. Space Science Board, Venus: Strategy for Exploration, p. 4. 

55. Campbell 9 December 1993. 



PIONEERING ON VENUS AND MARS 1 65 



As far as ground-based planetary radar was concerned, the Purple Book applauded 
its success. "Virtually all our present knowledge of the radius, rotation, and surface of 
Venus has been obtained using ground-based radars," the Purple Book proclaimed. With 
resolutions ranging from 100 to 500 km, radar had revealed features, and even the lack of 
topographic relief, in the equatorial region of Venus. Including a radar system on a Venus 
probe would yield "maps similar in appearance and usefulness to photographic maps of 
the same region." 

Ironically, the Purple Book cautioned against imaging Venus with a spacecraft radar. 
It pointed out that such radar images would be "directly competitive with ground-based 
observations and would provide similar data." That point resurfaced later during plan- 
ning for Magellan. Although a spaceborne radar could cover more of the planet's surface, 
the Purple Book concluded that "it is not yet clear whether the high cost of the addition- 
al information could be justified." Not only would a spacecraft radar require "great weight 
and complexity" in order to compete with the resolution already achieved by ground- 
based radars, but the "rapidly improving capabilities of radar observatories on the earth 
to image Venus" made radar mapping of the planet from orbit "less important at the pre- 
sent time." The report reflected the anticipated benefits of the planned upgrade of the 
Arecibo telescope. 

While technological and cost constraints militated against an orbiting radar, a viable 
alternative, according to the Purple Book, was the Stanford bistatic radar method, specif- 
ically that mode in which a radar on Earth transmitted and a receiver on the spacecraft 
collected echoes. The Purple Book concluded that "bistatic-radar experiments, in con- 
junction with ground-based observations, can provide a significant insight into the details 
of the surface structure and electromagnetic properties of Venus." 

The recommendation to conduct a bistatic experiment was not surprising; Len Tyler 
of the SCRA was one of the 21 Purple Book scientists. Although Tyler planned to do some 
bistatic observations with Pioneer Venus, those plans fell by the wayside. Later, as 
Pettengill was writing a proposal for Pioneer Venus and was looking for scientists to join 
him, he invited Tyler. Tyler turned down the invitation because of his heavy commitment 
to the Voyager project. 

In addition to the bistatic experiment, the Purple Book recommended using a radar 
altimeter to measure surface relief. Radar altimeter readings would complement the equa- 
torial topographic information available from ground-based radar observations, and a 
simple, low-power orbiting radar could measure vertical relief over those portions of the 
planet not covered by ground-based radars. 56 Using the altimeter to gather relief mea- 
surements was the cheapest and technologically least complicated alternative. In the end, 
a modified version of this approach was to fly on Pioneer Venus. 

After Venera 7 succeeded in transmitting data from the surface of Venus for 23 min- 
utes on 15 December 1970, a special panel reviewed the Purple Book conclusions. Their 
recommendation, to make no changes in the Purple Book, opened the door for NASA to 
issue an Announcement of Opportunity in July 1971 for scientists to participate in defin- 
ing the Venus program. 57 

NASA established the Pioneer Venus Science Steering Group in January 1972, in 
order to enlist widespread participation of the scientific community in the early selection 
of the science requirements for the Pioneer Venus project. The Science Steering Group 
met with Pioneer Venus project personnel between February and June 1972. The Group 
developed in great detail the scientific rationale and objectives for several voyages to 
Venus and outlined candidate payloads. 58 



56. Tyler 10 May 1994; Simpson 10 May 1994; Venus: Strategy for Exploration, pp. 58-62. 

57. Fimmel, Colin, and Eric, pp. 17-18. 

58. Fimmel, Colin, and Burgess, p. 18. 



1 66 TO SEE THE UNSEEN 



The search for mission objectives stirred radar astronomer Gordon Pettengill to pro- 
pose a radar experiment for the mission. Pettengill recalled: "I remember doing a calcu- 
lation literally on the back of an envelope. I realized that if we could get even a tiny little 
antenna into a reasonable orbit around Venus, we could do an awful lot in terms of 
measuring the altitude and the reflecting properties of the surface. ...By going around 
Venus in a polar, rather than an equatorial orbit, we could get a totally new view of Venus. 
We could detail the whole surface, instead of just the equatorial band that we observed at 
Arecibo." 

Pettengill then began "beating the drums" to include a radar experiment in the 
Venus program. 'The Science Working Group studied the concept. I didn't think I was 
going to survive that," he recalled. "Pioneer Venus was strictly an atmospheric mission. A 
radar experiment to study the surface stood out like a sore thumb." Nonetheless, NASA 
awarded Pettengill funds to conduct a feasibility study of a radar to image Venus. 59 

Above all else, the prime mission of Pioneer Venus was to study the planet's atmos- 
phere. An article published in 1994 in Scientific American 60 evaluated the scientific achieve- 
ments of Pioneer Venus and emphasized its contributions to atmospheric science, but 
failed to mention the radar experiment. Peter Ford, who collaborated with Pettengill on 
the Pioneer Venus radar experiment, pointed out that the Scientific American article's 
emphasis on the atmospheric science balanced the record; during the first three years of 
the Pioneer Venus mission, most publicity had focused on the radar imaging. 61 

Next, the Science Steering Group published its comprehensive report, called the 
Orange Book. Among the 24 areas of research advocated, only one was related to the plan- 
et's surface. As the project evolved, Pioneer Venus matured into a single-opportunity mis- 
sion with a multiprobe and an orbiter. In September 1972, NASA disbanded the Science 
Steering Group and issued an Announcement of Opportunity for scientists to participate 
in the multiprobe mission. Not until August 1973 did NASA issue an Announcement of 
Opportunity for the orbiter. Over the ensuing months, the NASA Instrument Review 
Committee evaluated proposals for orbiter scientific payloads, including Pettengill's radar 
experiment, then presented its recommendations to NASA Headquarters in May 1974. 
When NASA selected the final orbiter payloads on 4 June 1974, the radar experiment was 
among them. 

The radar was only one of 12 scientific instruments on the orbiter. In contrast to the 
spaceborne radar initially developed at MIT, which was to consume no more than 100 
watts and weigh less than 50 pounds, the Pioneer Venus radar required only 18 watts and 
weighed 9.7 kilograms (21.3 pounds). "You could literally put the thing under one arm 
and carry it," as Pettengill characterized it. Compared to other instruments on Pioneer 
Venus, though, 9.7 kilograms was an appreciable load; it accounted for 22 percent of the 
total weight (45 kilograms) of all 12 orbiter scientific instruments. 62 

Although the radar experiment, in Pettengill's words, "stood out like a sore thumb," 
NASA Headquarters wanted to see the surface features of Venus through its white, sulfu- 
ric-acid clouds. The information was a vital part of planning for a future mission to Venus 
to map the planet's surface, known eventually as Magellan. The only reason the radar 
experiment stayed on Pioneer Venus, according to Pettengill, was that Advanced 
Programs at NASA Headquarters wanted it, even though its inclusion made life "a little 
uncomfortable for the other experiments." 63 



59. Pettengill 28 September 1993. 

60. Janet G. Luhmann, Pollack, and Colin, "The Pioneer Mission to Venus," Scientific American 270 (April 
1994): 90-97. 

61. Ford 3 October 1994. 

62. Pettengill 28 September 1993; Fimmel, Colin, and Burgess, pp. 18-21, 38 and 58. 

63. Pettengill 28 September 1993. 



PIONEERING ON VENUS AND MARS 167 



The key individual in NASA's Office of Advanced Programs who supported Pettengill 
and the radar experiment was Daniel H. Herman. Before joining NASA in 1970 as head 
of Advanced Programs in the Office of Lunar and Planetary Programs, Herman had 
worked at Northrup on the development of surveillance synthetic aperture radar (SAR) 
mappers for the Navy, specifically investigating the feasibility of transmitting reconnais- 
sance data in real time. At NASA, his job was to develop new missions and to "sell" them 
through the NASA hierarchy and ultimately to the President and Congress. Danny 
Herman's job, then, was to sell the Pioneer Venus mission. In Pettengill's words, Herman 
was "an eminence grise" and "a supersalesman." As early as 1972, Danny Herman also 
began to put together and push the Magellan project. 64 

Unlike Magellan, Pioneer Venus strictly speaking did not have a synthetic aperture 
radar; instead, the radar altimeter had a mapping mode. The most valuable data returned 
from the Pioneer Venus radar experiment would be the extensive topographical infor- 
mation acquired by the altimeter. The mapping mode did generate crude, low resolution 
images of portions of the planet's surface. 

Far more impressive were the images generated by synthetic aperture radars (SARs) 
mounted on aircraft and regularly utilized by geologists to study the geology and topog- 
raphy of Earth. The use of SARs in Earth geology was but one part of a long and complex 
history that stretched from the interpretation of aerial photographs to the emergence of 
remote sensing, an all-encompassing term which has came to involve the interpretation of 
infrared, ultraviolet, microwave, gamma ray, and x-ray images, as well as optical pho- 
tographs. 

Radar Geology 

Radar geology, as the study of geologic surface features from radar maps has come 
to be called, had its roots in the military surveillance radar research of the 1950s. It began 
to find a home in NASA during the 1960s and found a common bond with planetary radar 
astronomy in the 1970s, thanks largely to Pioneer Venus and Viking. The trickle of astro- 
geologists converted to planetary radar images by Pioneer Venus and Viking swelled 
through purposeful steps taken in the planning of Magellan to bring together planetary 
geology and planetary radar investigators. 

By World War I, aerial photography had become a key tool in gathering military 
intelligence. The scientific applications of photointerpretation grew after the war, partic- 
ularly during the 1930s. Government agencies, such as the Agricultural Adjustment 
Administration, the Forestry Service, and the Tennessee Valley Authority, began to use 
aerial photographs, and the USGS entered the field of photogrammetry, the making of 
maps from photographs, with a series of geologic and topographic maps constructed from 
aerial photographs. 65 

After World War II, the military sponsored research on two types of Side-Looking 
Airborne Radar (SLAR) used in remote sensing and especially for surveillance. One type, 
known as real-aperture or incoherent radar, relied on transmission of a narrow beam to 
provide fine image resolutions in the direction parallel to the flight of the aircraft. The 
other type, known as synthetic aperture radar (SAR), relied on coherent data processing 
to synthesize a very large effective aperture in the direction of motion and, thereby, to 
provide a very narrow corresponding antenna beam. Continuously operating SARs 
achieve a surface resolution that is independent of wavelength and approximately equal 
to their along-orbit physical antenna dimension. Normally, in real-aperture radars, 



64. Pettengill 28 September 1993; Daniel H. Herman, telephone conversation, 20 May 1994. 

65. William A. Fischer, "History of Remote Sensing," in Robert G. Reeves, Manual of Remote Sensing (Falls 
Church, Virginia: American Society of Photogrammetry, 1975), [2 volumes] vol. 1, pp. 27-39. 



1 68 TO SEE THE UNSEEN 



resolution is better the shorter the wavelength. In order to achieve high resolution, SARs 
replace the need for a large aperture with a large amount of data processing. 66 

The military branches developed SARs in the 1940s and 1950s under highly classi- 
fied conditions in corporate and university laboratories, such as those at the Goodyear 
Aircraft Corporation, the Philco Corporation, the University of Illinois Control Systems 
Laboratory, and the University of Michigan Willow Run Research Center. By the late 
1950s, a number of experimental SAR systems emerged, such as the one built by Texas 
Instruments for the Army. In 1961, under Air Force contract, Goodyear built the first 
operational SAR system; it had a resolution of about 15 meters. Throughout the 1960s, 
Goodyear and other firms began to commercialize SAR applications. 67 

A series of symposia underwritten by the Office of Naval Research (ONR) and held 
at the University of Michigan, where a great deal of SLAR work took place under contract 
with the ONR, greatly stimulated and advanced radar geology. 68 The University of 
Michigan symposia series grew out of a study initially recommended by a subcommittee of 
the National Academy of Sciences (which soon formed the Committee on Remote 
Sensing of Environment) and the Geography Branch of the ONR. A group from the ONR 
and the National Academy of Sciences met in January 1961 to discuss the need for more 
advanced and efficient data acquisition techniques in the Earth sciences. Although 
University of Michigan faculty dominated the first symposium, held in February 1962, 
subsequent symposia participants reflected the spreading commercial importance of SAR 
systems in studying the Earth. By the third symposium, held in October 1964, the empha- 
sis had shifted to remote sensing from weather and other satellites. 69 

During the third University of Michigan symposium, held in October 1964, R. F. 
Schmidt of the Avco Corporation, Cincinnati, presented a theoretical study on the feasi- 
bility of imaging Venus's surface with a radar. Schmidt failed, however, to address such 
practical questions as weight and power requirements. 70 Nonetheless, it was clear that 
those interested in remote sensing, and in radar imaging in particular, were open to the 
idea of imaging Venus from a spaceborne radar. 

Meanwhile, commercial applications of SARs to geology and topography expanded. 
The successful radar mapping of Panama in 1967-1968 by Westinghouse in Project RAMP, 
considered to be one of the major achievements in radar geology, further stimulated com- 
mercial radar mapping. In late 1971, Westinghouse surveyed the entire country of 
Nicaragua, and that same year the Aero Service/Goodyear RADAM Project (RADar of the 
AMazon), initially intended to cover only 1.5 million square kilometers, eventually cov- 
ered the entire country of Brazil, over 8.5 million square kilometers. RADAM was consid- 
ered the most impressive radar mapping program ever conducted. 71 



66. For a discussion of space SARs by one of its leading practitioners, see Charles Elachi, Spaceborne 
Radar Remote Sensing: Applications and Techniques (New York: IEEE Press, 1987). 

67. Fischer, pp. 42-43; Allen M. Feder, "Radar Geology, the Formative Years," Geotimes vol. 33, no. 11 
(1988): 11-14. See alsojohnj. Kovaly, Synthetic Aperture Radar (Dedham, MA: Artech House, Inc., 1976), Chapter 
One. I am grateful to Louis Brown for this last reference. 

68. Feder, p. 12. 

69. Proceedings of the First Symposium on Remote Sensing of Environment (Ann Arbor: University of Michigan 
Institute of Science and Technology, March 1962). Of the 72 participants, 37 of them, or 51%, were University 
of Michigan faculty. Proceedings of the Second (Ann Arbor: University of Michigan Institute of Science and 
Technology, February 1963); Proceedings of the Third Symposium (Ann Arbor: University of Michigan Institute of 
Science and Technology, October 1964); Proceedings of the Fourth Symposium (Ann Arbor: University of Michigan 
Institute of Science and Technology, June 1966). 

70. Peter C. Badgley, The Applications of Remote Sensors in Planetary Exploration," in Proceedings of 
the Third Symposium, pp. 9-28; R. F. Schmidt, "Radar Mapping of Venus from an Orbiting Spacecraft," ibid., pp. 
51-61. 

71. Feder, p. 13; H. MacDonald, "Historical Sketch: Radar Geology," pp. 23-24 and 27-28 in Radar 
Geology: An Assessment Publication 80-61 (Pasadena: JPL, 1 September 1980). This was a report of the Radar 
Geology Workshop, held at Snowmass, Colorado, 16-20 July 1979. 



PIONEERING ON VENUS AND MARS 1 69 



Parallel with the development of SAR mapping of Earth was the rise of astrogeology 
within the USGS in the late 1950s in response to a shortage of funds and a surplus of geol- 
ogists within the Survey. Following the discovery of an abundant supply of uranium ore in 
New Mexico, the USGS uranium project closed down in 1958. Eugene Shoemaker, a geol- 
ogist who moved to the USGS Pacific Coast Regional Center at Menlo Park, California, fol- 
lowing the closure of the uranium project, suggested lunar geologic mapping as one way 
to help alleviate the money and personnel problems. 

Shoemaker, who did his dissertation on Meteor Crater, sold lunar geologic mapping 
to NASA, which in contrast to the USGS had funding but too few geologists. The result 
was the creation of the Astrogeologic Studies Group, USGS, Menlo Park, on 25 August 
1960. Later, Shoemaker led a group of astrogeologists to a new location in Flagstaff, 
Arizona. 72 In 1963, geologist Peter C. Badgley came to NASA from the Colorado School 
of Mines. Badgley was interested in techniques for observing Earth from space, particu- 
larly to support the Apollo program. He let out contracts to firms, such as Westinghouse, 
and universities, especially the University of Michigan, to carry out radar geologic studies 
from aircraft. Moreover, Badgley continued to shift NASA money to the USGS to fund 
lunar and planetary geology. 73 Thus, the evolution of the NASA space program and the 
USGS astrogeology branch marched forward in tandem. 

During the Apollo program, certain USGS astrogeologists began collaborating with 
radar astronomers Stan Zisk and Tommy Thompson. Among them were Henry John 
Moore II, Shoemaker's former field assistant and part of the Menlo Park Astrogeologic 
Studies Group, and Gerald G. Schaber, UCLA and USGS Flagstaff. 74 These early lunar 
efforts involved radar mapping and topographical data collected from ground-based 
radars, not abstract data on rms slope and dielectric constant. Schaber collaborated with 
Tyler on interpreting lunar bistatic radar results, which were expressed in abstract math- 
ematical terms. Schaber admitted, "I never really did much with the interpretation of 
bistatic radar, because it is kind of a theoretical interpretation I don't really understand 
too much." 75 

The launch of SEASAT in the summer of 1978 began the era of satellite radar 
imagery. SEASAT demonstrated the feasibility of radar observations of Earth on a global 
basis, and initial examination of the SEASAT radar data indicated that one could fruitful- 
ly apply the data to a variety of problems in geology, agriculture, hydrology, and oceanog- 
raphy, as well as to planetary exploration. 76 

In order to assess the application of radar imaging to terrestrial geologic problems 
and to make recommendations to NASA, JPL sponsored the Radar Geology Workshop in 
Snowmass, Colorado, 16-20 July 1979, with funding from NASA. Among those on the 
organizing committee were Harold Masursky, USGS, and R. Stephen Saunders, JPL, who 
later played a role on Magellan. The workshop focused on radar observations of Earth, 
not the planets. 77 

Thus, by the launch of SEASAT in 1978, the year also of Pioneer Venus's launch, a 
good number of geologists were familiar with and could interpret radar images of Earth 
made from aircraft. But those geologists were more interested in terrestrial than extrater- 
restrial geology. On the other hand, through the pioneering efforts of Gene Shoemaker, 
the USGS Astrogeologic Studies Group already had embraced lunar radar geology. The 



72. Wilhelms, pp. 37-40, 43, 46, 48 and 77. 

73. Pamela E. Mack, Viewing the Earth: The Social Construction of the Landsat Satellite System (Cambridge: 
The MIT Press, 1990), pp. 46-49; MacDonald, pp. 26 and 28-29. 

74. Wilhelms, p. 47; Thompson 29 November 1994. See, for instance, Shapiro, Stanley H. Zisk, Rogers, 
Slade, and Thompson, "Lunar Topography: Global Determination by Radar," Science 17 (1972): 939-948. 

75. Schaber 27 June 1994. 

76. John P. Ford, "Seasat Orbital Radar Imagery for Geologic Mapping: Tennessee-Kentucky-Virginia," 
American Association of Petroleum Geologists Bulletin 64 (1980): 2064-2094; Radar Geology: An Assessment, p. 1. 

77. Radar Geology: An Assessment, passim. 



170 



TO SEE THE UNSEEN 




Figure 27 

SEAS.\T image of Death Valley, Earth. The launch ofSEASAT in 1978 began the era of satellite radar imagery. The resolu- 
tion of images made by military surveillance satellites was much finer, however. Utilization ofSEASAT technology was a basic 
strategy adopted byJPL in the planning of VOIR (later Magellan). (Courtesy of Jet Propulsion Laboratory, photo no. P-30224.) 

potential for planetary geologists and planetary radar astronomers to work together 
already had been realized in the Apollo program through the work of Stan Zisk and 
Tommy Thompson. The NASA Pioneer Venus working committees brought together 
additional radar astronomers and geologists. 

Once NASA decided the Pioneer Venus payloads and science experiments in June 
1974, the space agency created the Orbiter Mission Operations Planning Committee. 
Among its members were USGS astrogeologist Hal Masursky and radar astronomer 
Gordon Pettengill. They also worked together closely in the Surface-Interior Working 
Group, one of the six mission Working Groups responsible for developing key scientific 
questions. Hal Masursky chaired that Working Group (Table 4). 78 



78. Fimmel, Colin, and Burgess, pp. 22 and 218. 



PIONEERING ON VENUS AND MARS 



171 





Table 4 
Pioneer Venus Surface/Interior Working Group 




Scientist 


Institution 


Harold Masursky 
C.T. Russell 
Gordon H. Pettengill 
William M. Kaula 
George E. McGill 
RogerJ. Phillips 
Irwin I. Shapiro 


US Geological Survey 
University of California, Los Angeles 
Massachusetts Institute of Technology 
University of California, Los Angeles 
Massachusetts Institute of Technology 
Lunar and Planetary Institute 
Massachusetts Institute of Technology 





Pioneer Venus 

Without the radar experiment, Pioneer Venus would not have brought together 
planetary geologists and radar astronomers. Attending meetings of the Working Groups, 
as well as all mission meetings, was vital to the survival of the radar on a project whose 
prime objectives were atmospheric. As Pettengill explained: "It was a very demanding pro- 
ject that had to be watched closely. I had to make sure that we did not lose radar capabil- 
ity. We were fighting with 1 1 other Principal Investigators on Pioneer Venus. It was very 
important that I never miss a meeting. If I missed one meeting, those guys might come to 
some decision that would compromise the experiment." 

The Pioneer Venus atmospheric experiments competed with the radar experiment 
for spacecraft parameters. The atmospheric scientists wanted a different set of orbits and 
a different allocation of down link data bits. "It was a jungle out there!" Pettengill recalled. 
"You had to have a certain number of bits, or you could not do your work. If you turned 
your back, literally if you missed one meeting, they could make a decision to allocate 20 
percent of that particular format to some experiment instead of only 10 percent. Then 
you have lost that 10 percent. In 1975, especially, all of this was coming together. I could- 
n't miss a meeting. It really was taking up my time." 79 

The data handling system on the orbiter integrated all analog and digital telemetry 
data into formats for transmission back to Earth. Telemetry storage, playback, and real- 
time rates varied. The orbiter had a total of 14 telemetry formats; some were used during 
periapsis, others during apoapsis. The radar was a heavy user of two formats designed for 
use at periapsis, and in fact it used more of those two formats than any other experiment. 

NASA procured scientific instruments for Pioneer Venus in a variety of ways. 
Normally, the principal investigator was responsible for an instrument's design and 
construction. Either his own laboratory or a subcontractor built the instrument. NASA 
used a different procurement method for the Pioneer Venus radar. The project office at 
Ames Research Center built it for a radar team headed by Pettengill. Carl Keller, an Ames 
Research Center engineer, had overall decision-making responsibility, and the instrument 
prime contractor was the Hughes Aircraft Company Space and Communications Group, 
El Segundo, California, as a result of an open bid procurement. Pettengill characterized 
Carl Keller as an engineer from "the old school, a seat-of-the-pants, no nonsense teuton- 
ic. He would look at all the details. He was the right guy for the job. I enjoyed working 
with him. Not everybody did." 80 



79. Pettengill 28 September 1993. 

80. Pettengill 28 September 1993; Fimmel, Colin, and Burgess, pp. 22, 41 and 43. 



1 72 TO SEE THE UNSEEN 



Both MIT's Center for Space Research, with which Pettengill was associated, and JPL 
competed for the Pioneer Venus radar contract. The rivalry between MIT and JPL was 
tense, "a real Shootout" in Pettengill's words. At JPL, Walter Brown had been working on 
a Venus orbiter radar since the 1960s. His approach, however, differed considerably from 
that of MIT. 

Walter Brown's radar proposal involved placing a 100-MHz (3-meter) transmitter on 
the Pioneer Venus orbiter, while Pettengill and the MIT Center for Space Research pro- 
posed a 1,757-MHz (17-cm) system. The MIT antenna was directive, so that when the 
spacecraft rotated, it took data for only a fraction of each 12-second rotation of the space- 
craft. 81 

As Pettengill reflected: "Meanwhile, JPL thought they had the inside track. They 
were a NASA center, after all, and this was a NASA project. If I have a fault to lay on JPL, 
it is that they think that there is no place else in the world that does things as well as they 
do. They think they deserve the first cut of everything, because they are so much better 
than everybody else. They don't take kindly to new ideas that are not in-house; not invent- 
ed here is very much a JPL hallmark. Irwin Shapiro has fought this on the Planetary 
Ephemeris Program. We fought it on radar work, and Stanford has fought it. It has been 
difficult over time. JPL is so institutionalized into thinking that no one else can do any- 
thing but them. It has been an uphill battle over the years. It has put grey hairs on Von 
Eshleman's head; it certainly put a few on mine." 

JPL lost the radar battle. Their design would have bathed the whole spacecraft, even 
the solar panels, in radiation from the radar. The antenna extended all around the space- 
craft, so that as the spacecraft rotated, the radar always was transmitting. To Walter Brown, 
that was the advantage, but it made the electronics engineers nervous. 

In the end, neither MIT nor JPL built the Pioneer Venus radar, but it is typical of the 
kinds of fights for hardware contracts that mark NASA space missions. The winner of the 
contract was Hughes. Hughes devised a method by which the radar altimeter could image 
the planet's surface at low resolution with a small, 38-cm-diameter antenna. The elec- 
tronics of the MIT design were clumsy, Pettengill admitted, whereas the Hughes proposal 
was 'Very clever and efficient." 

"If we had done the experiment," he mused, "it probably would not have stayed in. 
I have to hand Hughes some credit for that. They really had a flash of insight into a clever 
way of instrumenting it.. ..They had a good team, and so did we. The main reason Hughes 
won was that they were willing to take a loss." For Hughes, taking a loss on the Pioneer 
Venus radar contract was a gambit to gain leverage on the Magellan radar contract, which 
they ultimately won. "At the time," Pettengill recalled, awarding Hughes the radar map- 
per contract "hurt a bit. I was hoping to get the hardware here at the Center for Space 
Research." 

In August 1974, Congress approved Pioneer Venus as a new start for fiscal 1975, and 
in November 1974, NASA made the final contract award to Hughes Aircraft Company. By 
1975, only three years away from launch, Pettengill recalled, "it all came together. With 
the Hughes contract, we started cutting metal." 83 On 20 May 1978, the orbiter left Cape 
Kennedy, followed atop a second Adas-Centaur rocket by the multiprobe on 8 August 
1978. Both reached Venus in early December 1978. 84 

The radar was a complicated instrument capable of operating in one of two modes, 
altimeter or mapper. It was a 1 ,757-MHz ( 1 7-cm) radar with a peak output of 20 watts and 
utilized relatively long pulses to improve the signal-to-noise ratio. Such a radar could not 



81. Pettengill 28 September 1993; Memorandum, Brunk, 29 November 1966, NHOB. 

82. Pettengill 28 September 1993. 

83. Pettengill 28 September 1993. 

84. Fimmel, Colin, and Burgess, pp. 27 and 35. 



PIONEERING ON VENUS AND MARS 1 73 



have performed planetary radar astronomy experiments from Earth, but reducing the dis- 
tance to the target made all the difference. 

Shortly after its encounter with Venus, the orbiter began making altimeter measure- 
ments of surface relief. The altimeter measured the distance from the orbiter to the plan- 
et's surface. In order to ascertain the height and depth of surface features, that distance 
was subtracted from the spacecraft's orbital radius, that is, the distance between the space- 
craft and the planet's center of mass. The Deep Space Network, while maintaining two- 
way communications with the spacecraft, generated radiometric data from which JPL 
accurately calculated its orbit, and the MIT group then used both the orbital and radar 
data to determine the radius of the planet at discrete positions on the surface. 

In the radar mapper mode, the instrument compensated for the complex motion of 
the spacecraft. Because the orbiter spun on its own axis about five revolutions per minute, 
radar observations took place only periodically, about one second out of each 12-second 
spin of the orbiter. The radar mapper also automatically compensated for the Doppler 
shift caused by the motion of the orbiter relative to the planet. 

The instrument took altimeter data, whenever the orbiter was below 4,700 km, and 
imaging data, when the orbiter was below 550 km, subject to competition with other 
experiments for the limited telemetry capacity. In order to minimize telemetry require- 
ments, the orbiter processed the radar echoes on board the spacecraft. The radar mapper 
achieved its best resolution, a footprint 23 km long and 7 km wide, at periapsis. The radar 
data also provided information on surface roughness and electrical conductivity. 85 

The radar mapper's first sweeps showed a region of Venus previously unexplored by 
ground-based radar. With the exception of a deep trench near the equator, the surface of 
Venus appeared relatively flat, similar to the Earth's surface and quite different from the 
rough, cratered surfaces of Mars, Mercury, and the Moon. Pioneer Venus continued to 
complete one orbit per day, when on the 14th orbit, the radar mapper began to malfunc- 
tion; data was lost. Scientists and engineers failed to find a remedy. Mission control turned 
off the radar for about two weeks around Christmas and the New Year. When mission con- 
trol turned on the radar mapper, they discovered that it worked, though not quite nor- 
mally. 

The problem, eventually traced to a timing malfunction that resulted from a differ- 
ential "aging" rate in two interconnected semiconductor devices, appeared when the 
instrument operated longer than ten hours. Pettengill, the experiment team leader, and 
project personnel decided to operate the radar mapper intermittently. After about 10 days 
of intermittent operation, the instrument started to function normally on 20 January 1979 
(orbit 47) .86 

Somehow, though, the mission had to recover the lost data. Data recovery was not 
possible during the first extended mission (September 1979), because the Deep Space 
Network was handling communications with Pioneer 11 at Saturn, so it took place during 
the second extended mission, April-May 1980. The 10 other scientific instruments (the 
infrared experiment failed after a few months and never ran again) continued to transmit 
data back to Earth; the radar mapper, however, was turned off as planned after Orbit 834 
on 19 March 1981. 87 



85. Fimmcl, Colin, and Burgess, pp. 58-59 and 113-115; Pettengill, D. F. Horwood, and Carl H. Keller, 
"Pioneer Venus Orbiter Radar Mapper: Design and Operation," IEEE Transactions on Geosdence and Remote Sensing 
GE-18 (1980): 28-32; Pettengill, Peter G. Ford, and Stewart Nozette, "Venus: Global Surface Radar reflectivity," 
ScienceZn (1982): 640-642. 

86. Pettengill, Ford, Walter E. Brown, William M. Kaula, Carl H. Keller, Harold Masursky, and George 
E. McGill, "Pioneer Venus Radar Mapper Experiment," Science 203 (1979): 806-808; Colin, "The Pioneer Venus 
Program, " Journal of Geophysical Research 85 (1980): 7588-7589; Fimmel, Colin, and Burgess, p. 107; Pettengill, 
Ford, Brown, Kaula, Masursky, Eric Eliason, and McGill, "Venus: Preliminary Topographic and Surface Imaging 
Results from the Pioneer Orbiter," Sdence2Q5 (1979): 91-93. 

87. Colin, pp. 7589 and 7590; Fimmel, Colin, and Burgess, p. 191. 



1 74 TO SEE THE UNSEEN 



The processing and interpretation of Pioneer Venus altimeter and mapper data sets 
by the MIT group again brought together planetary geologists and radar astronomers. 
Peter G. Ford, Pettengill's colleague in the MIT Department of Earth and Planetary 
Sciences, was a central player in the MIT effort. A native of Britain, Peter Ford initially 
came to MIT to work in VLBI (Very Long Baseline Interferometry) radio astronomy with 
Irwin Shapiro. From 1977 to 1985, he worked on various aspects of the Pioneer Venus 
orbiting radar experiments, including their geologic interpretation, although his training 
was in nuclear physics. The USGS processed some of the data to create a three-dimen- 
sional effect which graphically revealed depressions and mountains. Key among the plan- 
etary geologists were Hal Masursky and Gerald Schaber of the USGS, Flagstaff, and 
George E. McGill, University of Massachusetts at Amherst. 

The collaboration of radar astronomy and planetary geology resulted in many 
important discoveries about the surface of Venus, although preliminary analysis showed 
that much more could be learned about the planet's geological history. The altimeter data 
was used to create a number of maps, including a topographic contour map, a shaded 
relief map, and a map showing relative degrees of surface roughness. The altimeter and 
radar mapper data sets were assembled and placed in position by computer; however, vari- 
ations from orbit to orbit were edited by hand then smoothed out by computer. 

In preparation for the mission, a preliminary map was compiled from ground-based 
images and used by mission operations for planning. For this map, Goldstone radar 
images were computer mosaicked, and images obtained at Arecibo were mosaicked from 
photographic copy. The scale of this map was 1:50,000,000. Once the Pioneer Venus data 
were in hand, the map was updated to combine the spacecraft and ground-based data. 

The radar altimeter yielded a topographic map covering 93 percent of the Venus 
globe, with a linear surface resolution of better than 150 km. Vertical measurement accu- 
racy exceeded 200 meters. Relief was expressed as a center-of-mass-to-surface radius. 
Extremes went from a low of 6,049 km to a high of 6,062 km. Despite these impressive 
extremes of surface height and depth, the Pioneer Venus data confirmed and greatly 
expanded previous Earth-based observations on the global smoothness of Venus relative 
to the Moon, Mars, and Earth. Only about five percent of the observed surface was ele- 
vated more than two km above the mean radius, 6,051.5 0.1 km. 

Radar astronomer Gordon Pettengill processed and interpreted Pioneer Venus 
altimeter and mapper data sets. Don Campbell at Arecibo, and Dick Goldstein and 
Howard C. Rumsey, Jr., at JPL, supplied ground-based radar images and digital tapes, 
many before publication. The Arecibo and JPL radar images were compiled into a 
mosaic for the Pioneer Venus Planning Chart that was used in mission operations. Their 
high-resolution, Earth-based radar-imaging data also was essential for the interpretation 
of the spacecraft images and altimetry data. Thus, ground-based radar astronomers were 
brought into the Pioneer Venus project, and association with the project facilitated radar 
astronomers' access to the Goldstone radar. 

The radar brightness and elevation extremes dominated the imaging and topo- 
graphic maps of the highlands province, which included Ishtar Terra, Aphrodite Terra, 
and Beta Regio. The two highland regions, Ishtar and Aphrodite terrae, resembled ter- 
restrial "continents" because they were high and had areas comparable to continents on 
Earth. Ishtar and Aphrodite appeared to be the size of continents, roughly equivalent to 
Australia and Africa, respectively. Beta, a much smaller feature initially detected with 
ground-based radar, appeared to differ from Ishtar and Aphrodite in roughness char- 
acteristics and possibly in age and chemical composition. Ishtar Terra was the most ele- 
vated region found on Venus. It included three topographic elements: Lakshmi Planum, 
a western plateau area; Maxwell Monies, the central mountainous area previously studied 



PIONEERING ON VENUS AND MARS 



175 



with Earth-based radars; and a complex eastern region. The highest point found on Venus 
was the summit of Maxwell Monies. Standing 11.1 km above the planet's average radius 
(in Earth terms, above sea level), Maxwell Monies was higher than Mount Everest, which 
reaches 8.8 km above sea level. The lowest poini found on Venus was a rifl valley or irench 
named Diana Chasma. 88 




Figure 28 

Pioneer Venus map of Venus, 1 980, showing A Ipha Regio and Maxwell Mantes, along the planet 's meridian, and Beta Hegio 
at longitude 280. Diana Chasma is at longitude 160. Compare this map with the Venus mosaic made from Arecibo 
Observatory radar observations (Fig. 30). (Courtesy of Jet Propulsion Laboratory, photo no. P45744.) 

The planetary radar and geology collaboration yielded a host of new topographical 
names. In order lo systematically standardize the names of Venus surface features, as well 
as those discovered earlier on Mars and the Moon, on an international level, the 
International Astronomical Union (IAU) created the Working Group for Planetary 
Sysiem Nomenclaiure (WGPSN) during iis 15th General Assembly at Sydney, 21-30 
August 1973. The IAU established the WGPSN because of ihe receni rapid advance in 
knowledge of the topography and surfaces of planetary bodies, as well as the necessity of 
coordinating ihe approved systems of nomenclature among the differenl planels and 
iheir salelliles. 



88. Fimmel, Colin, and Burgess, p. 154; Masursky, Eliason, Ford, McGill, Pettengill, Gerald G. Schaber, 
and Schubert, "Pioneer Venus Radar Results," Journal of Geophysical Research 85 (1980): 8232-8260; Pettengill, 
Eliason, Ford, George B. Loriot, Masursky, and McGill, "Pioneer Venus Radar Results: Altimetry and Surface 
Properties," Journal of Geophysical Research 85 (1980): 8261-8270; V-Gram no. 10 (January 1987): 20. 



1 76 TO SEE THE UNSEEN 



Unlike most other IAU working groups, the WGPSN did not report through any 
commission or group of commissions, but was responsible to only the IAU Executive 
Committee. The WGPSN was charged with formulating and coordinating all topographic 
nomenclature on the planetary bodies of the solar system and had certain powers of 
action in the interval between General Assemblies. Radar astronomer Gordon Pettengill 
was a member of the WGPSN. The Task Group for Venus Nomenclature, responsible for 
compiling the detailed material presented to the WGPSN, included Gordon Pettengill, 
chair, JPL radar astronomer Dick Goldstein, USGS geologist Hal Masursky, and the Soviet 
scientist M. Ya. Marov. 

Although the first meeting of the WGPSN, held in Ottawa, 27-28 June 1974, did not 
concern itself with the naming of surface features on Venus, at the second meeting, held 
in Moscow, 14-18 July 1975, the WGPSN named three valleys on Mercury Arecibo, 
Goldstone, and Haystack after the radar observatories and established two themes for 
naming Venus features. The first theme was the "feminine mystique long associated with 
Venus." Hence, for example, the continent-sized features Ishtar and Aphrodite were 
named for the Babylonian and Greek goddesses of love, respectively. 

The second theme arose from the "extensive and opaque cloud cover which sur- 
rounds the planetary sphere" which "requires the use of radio and other techniques in 
order to study and map the surface." Therefore, the WGPSN proposed "to assign the 
names of deceased radio, radar and space scientists to topographic features." One excep- 
tion, Alpha, was admitted. Alpha was one of the first Cytherean features to be observed 
"and which has served to help define the origin of the official IAU system of longitude for 
the planet." During subsequent meetings of the WGPSN, held in Grenoble, 30-31 August 
1976; Washington, 1-2 June 1977; Innsbruck, 2 June 1978; and Montreal, 13-15 August 
1979, the WGPSN approved not only Alpha, but Beta and Maxwell as well. 89 Thus, the fea- 
ture names first given by ground-based radar astronomers were fixed on the map of Venus. 

Pioneer Venus awakened more planetary geologists to the value of radar data, espe- 
cially radar images. Pioneer Venus also was a new taste of Big Science that would lead to 
the Magellan mission. In turn, Magellan culminated the linking of planetary geology with 
radar astronomy and further blurred the distinction made earlier in the history of plane- 
tary radar astronomy between ground-based radar and space exploration. 



89. Transactions of the International Astronomical Union 17A (1979): 113-114; "Working Group for 
Planetary System Nomenclature," Ibid. 16B (1977): 321-369; "Working Group for Planetary System 
Nomenclature," Ibid. 17B (1980): 285-304. 



Chapter Seven 

Magellan 



Magellan culminated the shift of radar astronomy toward planetary geology kindled 
by Apollo and fostered by Viking and Pioneer Venus with the creation of workshops and 
microsymposia. The workshops attempted to bridge the gap between radar and geologic 
knowledge among practitioners, while the microsymposia provided annual opportunities 
for U.S. and Soviet geology and radar scientists interested in Venus to exchange research 
results. This shifting of the planetary radar paradigm toward geology also manifested itself 
in articles co-authored with planetary geologists, publication in new journals, especially 
the Journal of Geophysical Research, and attendance at American Geophysical Union meet- 
ings. 

Furthermore, the close relationship between NASA missions and ground-based plan- 
etary radar astronomy that had developed at Haystack, Arecibo, and Goldstone since 1970 
continued with Magellan. The Arecibo and Goldstone radars observed Venus throughout 
the two decades spanned by Pioneer Venus and Magellan, and their data contributed to 
the success of those missions. In addition, the range-Doppler images created from that 
data also drew geologists to planetary radar astronomy. 

Magellan, like Pioneer Venus, was not ground-based planetary radar astronomy; it 
was space exploration. By carrying out imaging from a spacecraft, radar astronomer 
Gordon Pettengill had erased that distinction. That distinction no longer seemed to 
describe the field, as Len Tyler and Dick Simpson joined the Magellan radar team. Tyler 
and Simpson had not abandoned bistatic radar and radio occultation experiments; they 
had simply added Magellan radar science to their wide range of research interests. 

Unlike the Pioneer Venus mission, or the Goldstone and Arecibo facilities, Magellan 
was not a case of radar astronomy "Little Science" piggybacking onto a Big Science facili- 
ty. Magellan was Big Science. Moreover, its single scientific instrument was a radar. The 
Smithsonian push to have Congress fund the NEROC 440-ft (134-meter) dish never 
reached the floor. With Magellan, then, Congress considered for the first time under- 
writing construction of a facility dedicated primarily to planetary radar astronomy, albeit 
one whose lifetime was rather limited. Magellan illustrates the range of factors that influ- 
ence the scientific conduct and outcome of a Big Science project. The change of admin- 
istration in 1980, Cold War politics, and the Challenger accident, as well as ongoing and 
changing budgetary and technological constraints largely shaped the scale and scope of 
the Magellan mission and its science. 

AllezVOIR! 

As a mission concept, Magellan began in 1972, when Danny Herman, the head of 
NASA Advanced Programs, convened an informal meeting of scientists, including Gordon 
Pettengill, NASA engineers, and representatives of several key aerospace companies at the 



177 



1 78 TO SEE THE UNSEEN 



Denver division of Martin Marietta Aerospace, to discuss putting a synthetic aperture 
radar on a spacecraft to Venus. 1 

Subsequently, two NASA laboratories, Ames Research Center and JPL, organized 
study groups and began planning the mission and appropriate spacecraft parameters. At 
Ames, Byron Swenson and John S. McKay put together a study group that worked closely 
with Martin Marietta Aerospace in planning a Venus SAR mapping mission. They initially 
proposed a variation on Pioneer Venus with an elliptic orbit. During the period 1972 
through 1974, Ames Research Center, Martin Marietta Aerospace, and the Environmental 
Research Institute of Michigan (ERIM) , which had been involved in the development of 
airborne SAR systems for the military as early as the 1950s, carried out a preliminary eval- 
uation of data handling problems and techniques. The 1974 joint report of Martin 
Marietta Aerospace and the ERIM defined the project's science requirements and argued 
in favor of a circular orbit. 2 

At the same time, a similar study was underway at JPL under Louis D. Friedman. In 
order to distinguish their Venus project from that of the Ames group, Friedman and Al 
Laderman named the JPL project the Venus Orbiting Imaging Radar (VOIR). Laderman 
had played a key role in the development of the SEASAT SAR. He and Friedman intend- 
ed the acronym to connote the sense of the French verb "voir," meaning to see. VOIR was 
going to "see" the (optically) unseen surface of Venus. The JPL group included science, 
mission, and radar people. R. Stephen Saunders was the principal study scientist. Later, he 
became Magellan Project Scientist, as well as an investigator in the radar group. Saunders 
had served on the Viking Mission to Mars, before carrying out NASA-funded research in 
planetary geology and participating on the Shuttle Imaging Radar (SIR-A) project. 

The JPL group decided, mainly on the urging of Friedman, to use a circular orbit. A 
circular orbit would simplify the radar imaging process. The radar system always dealt with 
the same parameters, because it was always at the same height above the surface. 
Friedman felt that simplifying the radar versus the increased propulsion required to 
achieve a circular orbit was a good trade-off. Although the added propulsion needed to 
achieve a circular orbit would increase the overall cost of the mission, at least it was under- 
stood. The synthetic aperture radar was a new technology; an elliptical orbit presented a 
host of radar and data processing problems. Jim Rose's study group, charged with plan- 
ning the spacecraft, proposed a vehicle based on the Mariner system. The radar study 
group specified a radar system compatible with the 3-meter (10-ft) antennas built for the 
Pioneer missions to the outer solar system. Already, the goal was to economize by using 
existing technology. 3 

Many of the initial assumptions concerning look angle, number of looks, various res- 
olution assumptions, number of bits, and other radar system parameters came under crit- 
icism by scientists familiar with optical data, but nonetheless responsible for interpreting 
the radar data. Those criticisms led JPL to redesign away from the Mariner approach and 
to exploit internal strengths in synthetic aperture radars gained through the SEASAT pro- 
gram. Ultimately, the SEASAT experience gave JPL an edge over its competitors. 



1. Herman, telephone conversation, 20 May 1994. 

2. Memorandum, Louis D. Friedman toj. C. Beckman, "VOIR, Archeology, 10/79," Box 14 [hereafter 
Friedman-Beckman Memorandum] ; VOIR Historical Perspective, "VOIR, VOIR Mission, Briefing to NASA Code 
S, 5/78," Box 8; "VOIR, A Study of an Orbital Radar Mapping Mission to Venus, Vol. 1, 9/73," Box 10; "VOIR, 
Report, A Study of an Orbital Radar Mapping Mission to Venus, Vol. 2, 9/73," Box 14; "VOIR, Report, A Study 
of an Orbital Radar Mapping Mission to Venus, Vol. 3, 9/73," Box 14; and "VOIR, (NASA) Correspondence 
VOIR Mission Study Books, 10/77," Box 10, JPLMM. 

3. Friedman-Beckman Memorandum; VOIR Historical Perspective; "VOIR, Report, A Study of an 
Orbital Radar Mapping Mission to Venus, Vol. 2, 9/73," and "VOIR, Report, A Study of an Orbital Radar 
Mapping Mission to Venus, Vol. 3, 9/73," Box 14, JPLMM; V-Gram no. 9 (October 1986): 3; Campbell 
8 December 1993. 



MAGELLAN 



179 



SEASAT was an Earth-orbiting satellite equipped with a SAR and designed for 
oceanographic research. In its 1977 mission and systems study, JPL proposed the SEASAT 
SAR as the potential design base for the VOIR. JPL argued that SEASAT already had con- 
verted the concept of a spacecraft imaging radar into a reality. SEASAT used much of the 
conceptual and system design contained in the original JPL VOIR study, while later VOIR 
studies borrowed heavily from the SEASAT experience. JPL also contributed SEASAT 
staff. John H. Gerpheide, SEASAT satellite system manager, became VOIR/Magellan pro- 
ject manager. Anthony J. Spear, sensor manager on SEASAT, became VOIR/Magellan 
deputy manager. 4 

When the Science Working Group convened at NASA Headquarters in November 
1977, NASA already had selected the JPL study. NASA charged the Science Working 
Group with defining the major scientific objectives and rationale for a Venus orbiter 
equipped with a radar imager, as well as defining other experiments and defining the 
radar-imaging requirements of the mission, including coverage, resolution, operating 
wavelength, telemetry data rate, and data processing. The Science Working Group con- 
sidered the merit of global coverage at medium resolution and imaging selected areas at 
high resolution. 

The composition of the VOIR Science Working Group drew heavily on Pioneer 
Venus alumni and from both the planetary radar and geology communities (Table 5) . The 
planetary radar members were Don Campbell (Arecibo), Dick Goldstein (JPL), and 
Gordon Pettengill (MIT) , who chaired the Group. Harold Masursky and Gerald Schaber, 
both astrogeologists from the USGS, Flagstaff, and both participants in Pioneer Venus, 
also served on trie Science Working Group. 



Table 5 


VOIR (Magellan) Science Working Group 




Scientist 


Institution 






Gordon H. Pettengill, Chair 


MIT 






Harry S. Stewart, Executive Secretary 


JPL 






Donald B. Campbell 


NAIC, Cornell 






Richard M. Goldstein 


JPL 






William M. Kaula 


UCLA 






Michael C. Malin 


JPL 






Harold Masursky 
Norman Ness 


US Geological Survey 
Goddard Space Flight Center 






William L. Quaide, Program Scientist 
R. Keith Raney 


NASA Headquarters 
Canada Center for Remote Sensing 






William B. Rossow 


Princeton University 






R. Stephen Saunders, Project Scientist 


JPL 






Gerald G. Schaber 


US Geological Service 






Sean C. Solomon 


MIT 






David H. Staelin 


MIT 






A. Ian Stewart 


University of Colorado 






Robert Strom 


University of Arizona 






G. Leonard Tyler 


Stanford University 







The Science Working Group thus became a forum for reinforcing bridges between 
planetary radar and geology scientists. The geologists were 'Very helpful in teaching us 
radar people what it was that turned them on, as it were, while we were helpful to them in 
terms of optimizing the operation of the radar, so as to provide them with what they want- 
ed," Gordon Pettengill explained. 'This interaction shaped the specifications that turned 



4. Friedman-Beckman Memorandum; VOIR Historical Perspective; "VOIR, (NASA) Correspondence 
VOIR Mission Study Books, 10/77," Box 10.JPLMM; Robert C. Beal, Venus Orbiter Imaging Radar FY7 7 Study Report 
Radar Studies, Report 660-60 (Pasadena: JPL, 2 May 1977), pp. 5-1 through 5-18; V-Gram no. 9 (October 1986): 
2. On VOIR's SEASAT legacy, see also Murray, pp. 127-129. 



1 80 TO SEE THE UNSEEN 



into the VOIR and later the Magellan programs. The process is ongoing. It goes on even 
today." 5 

NASA was particularly mindful that the Science Working Group "take full account of 
the anticipated capabilities of Earth-based radar systems as well as the results expected 
from the Pioneer Venus experiments." 6 The Committee on Planetary and Lunar 
Exploration (COMPLEX) of the Space Science Board, and in particular its chairman, 
Caltech professor of geology and geophysics Gerald J. Wasserburg, was behind that 
request. The request was logical, Herman judged in retrospect. Given the high cost of 
VOIR, why should NASA and the Congress commit a large sum of money to a space mis- 
sion, when Arecibo could acquire the same imaging data for far less money? Having the 
1977 VOIR Science Working Group assess the science yield from a large ground-based 
radar telescope, like Arecibo, compared to the science yield from a spacecraft was, in 
Herman's words, 'Very necessary to yield off the devil's advocate question." 7 

Herman already had emphasized to the initial JPL study group the need to consider 
the capabilities of Arecibo for undertaking ground-based radar observations of Venus. 
The chief weakness in the development of the Venus radar orbiter concept, he explained, 
was the belief held by some scientists that upgraded ground facilities could provide data 
that was almost as good at a far lower cost. 

By 1977, range-Doppler imaging of Venus at Goldstone and Arecibo had advanced 
considerably thanks to the refinement of interferometry techniques and the attainment 
of finer image resolution. At Goldstone, for example, Dick Goldstein used a radar inter- 
ferometer, the 400-kilowatt Mars Station linked to a 26-meter Goldstone DSN antenna 
(DSS-13, known also as the Venus site) located about 22 km to the southeast, to observe 
and image Venus in 1972 for the first time and subsequently during the winter of 
1973-1974 and the summer and fall of 1975. Over that period, image resolution fell from 
15 to 10 km, although in some instances Goldstein realized resolutions as low as 5 to 9 km 
in the East-West direction and 7 to 10.8 km North to South. In 1977, Rayjurgens and Dick 
Goldstein organized a three-station interferometer; the Mars Station transmitted, then it 
and two 26-meter Goldstone DSN antennas (DSS-12 and DSS-13, the Echo and Venus 
sites, respectively) received. The three-station data yielded image resolutions of 10 and 
even down to 8 km. 8 

Planetary scientists R. Stephen Saunders and Michael C. Malin of the JPL 
Planetology and Oceanography Section studied the Goldstone Venus images and con- 
cluded that they revealed a complex and varied terrain. They found degraded impact 
craters and evidence for volcanism. In these radar images, Beta now appeared to be a 700- 
km-diameter region elevated a maximum of about 10 km relative to its surroundings with 
a 60-by-90-km-wide depression at its summit. Saunders and Malin tentatively identified 
Beta Regio as a shield volcano. 9 

Meanwhile at Arecibo, the radar upgrade from UHF to S-band increased the resolu- 
tion of Venus radar images abundantly. In 1969, with the old 430-MHz radar operating in 
an interferometric mode, Campbell, Rayjurgens, and Rolf Dyce achieved a resolution of 



5. Pettengill 29 September 1993. 

6. "VOIR, (NASA) Correspondence, VOIR Mission Study Books, 11/78," Box 13.JPLMM. 

7. Herman, telephone conversation, 20 May 1994. 

8. Herman, telephone conversation, 20 May 1994; Rumsey, Morris, R. Green, and Goldstein, "A Radar 
Brightness and Altitude Image of a Portion of Venus," Icarus 23 (1974): 1-7; Goldstein, R. Green, and Rumsey, 
"Venus Radar \m*%es," Journal of Geophysical Research vol. 81, no. 26 (10 September 1976): 4807-4817; Goldstein, 
R. Green, and Rumsey, 'Venus Radar Brightness and Altitude Images," Icarus 36 (1978): 334-352; Jurgens, 
Goldstein, Rumsey, and R. Green, "Images of Venus by Three-Station Radar Interferometry 1977 Results," 
Journal of Geophysical Research vol. 85, no. A13 (30 December 1980): 8282-8294. 

9. Saunders and Michael C. Malin, "Surface of Venus: Evidence of Diverse Landforms from Radar 
Observations," Science 196 (1977): 987-990; ibid., "Geologic Interpretation of New Observations of the Surface 
of Venus," Geophysical Research Letters 4 (1977): 547-550. 



MAGELLAN 



181 



only 300 km. An improved line feed brought Venus image resolution down to about 100 
km in 1972, the last Venus observations before the S-band upgrade. 10 

Concomitant with the S-band radar upgrade, the NAIC constructed a second anten- 
na, a 30-meter equatorially mounted reflector, at a site about 11 km to the north- 
northeast of the main 1,000-ft (305-meter) dish. Data taken by Campbell and Dyce in asso- 
ciation with Gordon Pettengill during the Venus inferior conjunction of late August and 
early September 1975 yielded images with surface resolutions approximating those of 
Goldstone, between 10 and 20 km. Especially interesting was a detailed view of Maxwell. 11 




Figure 29 

Radar image of Maxwell Monies made at Arecibo. Surface resolution is about 10 kilometers. Maxwell, which measures about 
750 kilometers from north to south, includes the planet 's highest elevation: 1 1 kilometers above the planetary mean. (Courtesy 
of National Astronomy and Ionosphere Center, which is operated by Cornell University under contract with the National Science 
Foundation.) 

Thanks to hardware improvements, Don Campbell and Barbara Ann Burns, his grad- 
uate student, increased the resolution of Venus images to five km during the 1977 inferi- 
or conjunction. For her doctoral dissertation, Burns used these radar images to study cra- 
tering on the planet. She and Campbell identified over 30 circular features in the images 
and tentatively classified them as craters, but the level of resolution did not permit them 
to ascertain whether their origin was volcanic or impact. 12 Also, in conjunction with USGS 



10. Campbell, Jurgens, Dyce, Harris, and Pettengill, "Radar Interferometric Observations of Venus at 
70-Centimeter Wavelength," Science 170 (1970): 1090-1092; NAIC QR Q2/1972, pp. 3-4, and Q3/1972, pp. 3-4. 

11. Campbell, Dyce, and Pettengill, "New Radar Image of Venus," Science 193 (1976): 1123-1124. 

12. Campbell and Barbara Ann Burns, "Earth-based Radar Imagery of Venus," Journal of Geophysical 
Research vol. 85, no. A13 (30 December 1980): 8271-8281; Burns, "Cratering Analysis of the Surface of Venus as 
Mapped by 12.6-cm Radar," Ph.D. diss., Cornell University, January 1982. 



182 



TO SEE THE UNSEEN 




Figure 30 

Large mosaic of Venus made from Arecilm radar observations. The image is centered on longitude 320 (see Fig. 28). Maxwell 
Mantes is the large white area in the upper right corner. Isft of center is Beta Regio. (Courtesy of National Astronomy and 
Ionosphere Center, which is operated by Cornell University under contract with the National Science Foundation.) 



MAGELLAN 183 



geologist Hal Masursky, Don Campbell and Gordon Pettengill studied images of Alpha, 
Beta, and Maxwell made from combined 1975 and 1977 Arecibo observations. 13 

As Campbell and fellow radar astronomers using the upgraded Arecibo telescope 
achieved resolutions as fine as 5 kilometers on Venus during the 1977 inferior conjunc- 
tion, the high resolution invited comparison with potential space-based radars. In order 
to evaluate the capabilities of ground-based radars versus orbiting radars, the JPL study 
group brought in Thomas Thompson. Thompson had conducted lunar radar work at 
both Arecibo and Haystack for the NASA Apollo program. As a result of Thompson's 
advice, as well as the counsel of Danny Herman, Friedman's study group framed a radar 
orbiter mission that complemented, rather than competed with, ground-based radar 
observations of Venus. 14 

Thompson judged that the best ground-based facility would be the upgraded 
Arecibo telescope. He concluded that the Earth-based radar was a very powerful tool for 
mapping the surface features of Venus. "We should encourage these efforts with great 
vigor," he wrote. "It seems certain that the Earth-based mapping will show many features 
that should be mapped in greater detail with the spacecraft. Also, the spacecraft will be 
needed to map the hemisphere of Venus which is not pointed toward Earth at each 
inferior conjunction." 15 

The combined revolutions of Venus and Earth around the Sun lead to an interval 
between inferior conjunctions (known as the synodic period) that nearly matches the spin 
rate of Venus about its axis, so that Venus presents almost the same hemisphere to Earth 
observers at inferior conjunction, the only moment when radar astronomers have 
sufficient signal-to-noise ratio to image the planet. 16 The major argument in favor of a 
spacecraft imaging mission to Venus was the inability of ground-based radars to image the 
planet's hidden hemisphere. A major upgrade of the Arecibo (or Goldstone) radar could 
have enabled it to observe and image Venus at orbital points before and after inferior 
conjunction. Such an upgrade would have cost less than the Magellan mission, and the 
improved radar would have been able to carry out radar research on a variety of other 
solar system targets. 

In 1977, NASA asked the VOIR Science Working Group to compare the costs of 
acquiring the data from a space-based SAR versus from a ground-based radar telescope, 
like Arecibo. "We knew that NASA did not want to hear that it would be cheaper, even 
though if you had taken what it actually cost to do Magellan and put it into a ground-based 
facility, you could have had one beautiful ground-based facility, and you could have 
endowed a fund to run it for years, forever probably, if you invested the money properly," 
Gordon Pettengill explained. 

Moreover, Pettengill argued, "As an investment in basic research, basic astronomy, a 
ground-based observatory would be a much wiser investment than sending Magellan out 
there. But that is not how things work. The money is available for the Space Station, but 
not available for any ground-based system that perhaps would do some of the same 
things." 17 

Pettengill assigned the tasks of comparing altimetry and radar imaging capabilities 
of ground-based versus space-based radars to Don Campbell and Dick Goldstein. They 



13. Pettengill, Campbell, and Masursky, The Surface of Venus," Scientific American 243 (August 1980): 
54-65. 

14. Thompson 29 November 1994; Friedman-Beckman Memorandum. 

15. Venus Orbiting Imaging Radar Study Team Report (Preliminary Draft (Pasadena: JPL, 31 August 1972), 
pp. 22-28, and Friedman and J. R. Rose, Final Report of a Venus Orbital Imaging Radar (VOIR) Study 760-89 
(Pasadena: JPL, 30 November 1973), Pettengill materials. 

16. For an explanation of the relationship between Venus's spin and rotational rates, see Goldreich and 
Peale, The Dynamics of Planetary Rotations," Annual Review of Astronomy and Astrophysics 6 (1968): 287-320. 

17. Pettengill 28 September 1993. 



1 84 TO SEE THE UNSEEN 



completed separate reports, with Goldstein considering altimetry and Campbell apprais- 
ing imaging capabilities. In each case, they compared a feasible radar design (an array 
located probably in Puerto Rico to have the planet nearly over head) with the current 
VOIR design requirements and judged whether the radar could achieve the geologic 
objectives of the Venus mission as well or better than the VOIR design. 

Campbell and Goldstein concluded that the radar array could do the VOIR science 
(almost) . The ground-based radar would not observe Venus at the same angles of inci- 
dence as VOIR, yet, because it would be able to observe Venus at a distance of 1.5 astro- 
nomical units, it could see the side of Venus hidden at inferior conjunction. The 100- 
meter resolution attainable from Earth was the same as that set for the VOIR mission. 
Moreover, the radar array could do the job for less. Pettengill decided to not include their 
conclusions in the Working Group report "for political reasons." He believed that NASA 
had no interest in the project, and that the conclusions might be embarrassing. 18 



Defining the VOIR 



In 1978, VOIR began to come together. The concept and preliminary design studies 
completed, the time had come to begin implementation studies. Radar development 
began in 1978 and took place in two stages, called Phase A, lasting from June through 
August 1978, and Phase B, October 1979 through June 1980. During Phase A, JPL 
received three proposals to study the VOIR SAR and selected one study contractor, 
Goodyear Aerospace Corporation. During Phase B, JPL received three proposals and 
selected two study contractors, Goodyear Aerospace Corporation and Hughes Aircraft 
Company. Participation in Phase B studies was important for those firms wishing to build 
the VOIR radar; implementation phase proposals were accepted from only those compa- 
nies participating in Phase B. 19 

The mission, its spacecraft and radar systems, and its science experiments underwent 
many revisions, and many of the risks foreseen in 1978 materialized before Magellan left 
Earth. As planned in 1978, the Space Shuttle would launch the VOIR spacecraft during 
the period May-June 1983. VOIR would arrive at Venus in November 1983 and spend five 
months in orbit, reduced from the earlier concept of a 19-month mission. JPL considered 
the possibility of the launch being delayed until 1984. Such a delay would cause an over- 
lap with Galileo, complicate scheduling the Deep Space Network, and raise costs. A 
delayed launch also would provide an opportunity for the Soviet Union to obtain Venus 
SAR images before the United States, thereby making VOIR radar results less interesting, 
if not inconsequential. 

The 1978 version of VOIR also exploited the availability of extant technology. In 
order to economize and facilitate selling and funding the project, VOIR would use com- 
ponents with proven performance records from other missions. For instance, from 
Mariner 10 VOIR borrowed its solar array and louvers, from Voyager its spacecraft elec- 
tronics, from Pioneer Venus its radar altimeter, and from SEASAT its synthetic aperture 
radar.so 

JPL hoped to make VOIR an in-house project. NASA had other ideas. In 1979, NASA 
stipulated that JPL contract out both the radar and the spacecraft to industry. NASA also 



18. Pettengill 3 October 1993. 

19. "VOIR, Venus Orbital Imaging Cost Review, 6/78," Box 5; "VOIR, Venus Orbiting Imaging Radar 
Review, 4/80," Box 10; and "VOIR, VOIR 88, Viewgraph Presentation to NASA Administrator, 11/87," Box 10, 
JPLMM. 

20. 'VOIR, Status Briefing to Committee on Planetary and Lunar Exploration, NASA Headquarters, 
6/78," and "VOIR, VOIR 84, Delayed Launch Option, 6/78," Box 3, JPLMM. 



MAGELLAN 185 



specified that the radar would have a single individual, from NASA, shoulder the respon- 
sibility of making it work. The NASA Headquarters decision had an immediate impact on 
VOIR design. The JPL in-house effort, which came to an end in February 1980, had con- 
centrated on using SEASAT technology. Now an industrial design would serve. In order 
to economize, JPL had proposed using the Galileo circular 4.8-meter antenna for both 
communications and the SAR. The weight of the Galileo antenna was significantly less 
than that of a competing antenna design. Instead, JPL now had to undertake a study of 
the competing and differing antenna patterns proposed by the contractors Goodyear and 
Hughes.2i 

In planning the VOIR radar mapper, the Science Working Group took into account 
the resolution of the images sent back by Mariner 9. Those images had revealed for the 
first time the diversity of Martian geologic structures, including young volcanoes, liquid 
cut channels, and large canyons of possible tectonic origin and had led to a fundamen- 
tally new understanding of the nature of Mars. The VOIR radar mapper had to have com- 
parable or better resolution than Mariner 9. Steve Saunders, project scientist, and Gerry 
Schubert, a geophysicist in the Department of Earth and Space Sciences, University of 
California at Los Angeles, originated the high-resolution design requirement. 22 

By 1978, the Science Working Group had defined four objectives for the 1984 VOIR 
mission: 1) images at a resolution and image quality equivalent to the Mariner 9 Mars mis- 
sion (100 percent of the surface at mapping resolution, 600 meters, and a few percent in 
a high resolution mode, 100 meters); 2) a global topographic map of the planet; 3) a 
global map of the gravity field; and 4) new investigations of the atmosphere and exos- 
phere. With surface exploration taking pride of place over atmospheric experiments, 
VOIR would be an inverse of Pioneer Venus. 

In October 1978, NASA dissolved the Science Working Group and issued an 
Announcement of Opportunity requesting proposals for VOIR science experiments in 
three categories: 1) surface and interior properties of the planet requiring use of the SAR 
and altimeter, 2) atmospheric and ionospheric and other geophysical experiments requir- 
ing flight instruments other than the SAR and altimeter, and 3) other geophysical, atmos- 
pheric, and general relativity experiments using existing spacecraft subsystems. 23 

Schooling potential users of Venus radar images became an integral part of the 
project. Project managers understood the VOIR radar image interpretation community as 
consisting of 70 investigators plus 130 associates with experience interpreting 
photographs of the Moon, Mars, and Mercury. In order to inculcate potential users in the 
interpretation of radar images, JPL planned two radar image interpretation sessions, ten- 
tatively scheduled with Goodyear, to take place in 1978 and 1979. NASA and JPL also were 
to sponsor studies based on the analogy between Venus radar images and radar images 
from aircraft and Earth satellites. 24 

After the release of the VOIR Announcement of Opportunity, experiment proposals 
began to arrive at NASA Headquarters. Gordon Pettengill submitted his proposal to use 
the synthetic aperture radar to image Venus in February 1979. Pettengill defined his radar 
experiment in such a way as to dovetail radar and geological science. The proposal 
focused on "those processes that have shaped the surface of Venus and that have led to 
the evolution of its distinctive atmosphere. A major intermediary in achieving this goal is 
the preparation of a global map of the surface morphology in sufficient detail to describe 
and locate the major geological types and processes exhibited by Venus." 



21. Pettengill 28 September 1993; "VOIR, Venus Orbiting Imaging Radar Review, 4/80," and "VOIR, 
Venus Orbiting Imaging Radar Review, 4/80," Box 10, JPLMM. 

22. A. Gustaferro to W. B. Hanson, 8 May 1979, "Magellan Documentation," NHO; Friedman-Beckman 
Memorandum; VOIR Historical Perspective. 

23. "VOIR, (NASA) Correspondence, VOIR Mission Study Books, 11/78," Box 13; "VOIR, Status 
Briefing to Committee on Planetary and Lunar Exploration, NASA Headquarters, 6/78," Box 3; and NASA, 
Announcement of Opportunity no. OSS-5-78, 12 October 1978, Box 13, JPLMM. 

24. "VOIR, Venus Orbital Imaging Cost Review, 6/78," Box 3, JPLMM. 



1 86 TO SEE THE UNSEEN 



Pettengill's proposal emphasized the general lack of knowledge about the surface 
features of Venus. Ground-based observations of Venus, Mariners 2, 5, and 10, the Soviet 
Venera missions, and Pioneer Venus all provided much information about the planet, but 
the proposal argued, 'This knowledge is heavily weighted toward the atmosphere of Venus 
and its interaction with the solar wind. Comparatively little is known about the solid sur- 
face or the interior of the planet." 

Pettengill's proposed team of co-investigators followed closely the membership of 
the disbanded Science Working Group. Apart from Arecibo radar astronomer Don 
Campbell, most co-investigators came from MIT's Center for Space Research, Pettengill's 
home organization, JPL, and the U.S. Geological Survey. Representing the USGS were 
Pioneer Venus veteran Hal Masursky, Gerald Schaber, then assistant chief of the Branch 
of Astrogeologic Studies, and Laurence A. Soderblum, chief of the USGS Branch of 
Astrogeologic Studies. Again, radar and planetary geologists associated in a common 
endeavor. 

Among the geologists who ultimately would be the most influential on the VOIR pro- 
ject was James W. Head, III, an associate professor in the Department of Geological 
Sciences at Brown University. Head had worked at NASA Headquarters for Bell 
Communications, a telephone company subsidiary that provided systems analysis and sup- 
port, including geologic work and landing site selection, to NASA on the Apollo missions. 
His research interests included comparative planetary geology, and he had been active in 
the geologic interpretation of radar data from the Moon for some years. More impor- 
tantly, as we shall see, he was a guest investigator on the Soviet Venera 15 and 16 missions. 

Pettengill proposed to organize his co-investigators into Task Groups that would par- 
ticipate in and monitor the design and implementation of all aspects of the SAR instru- 
ment, its operation during flight, and the reduction of imaging and ancillary radar data, 
as well as the subsequent geological and geophysical interpretation of the data. 25 

NASA received several other proposals, but they were not successful for one reason 
or another. H. MacDonald, a radar geologist at the University of Arkansas, proposed inter- 
preting VOIR data in the form of a radar landform atlas of Venus. The project largely 
duplicated the mapping contemplated in the Pettengill proposal. Another unsuccessful 
proposal came from Charles A. Barth, at the Laboratory for Atmospheric and Space 
Physics, University of Colorado, Boulder, to act as Principal Investigator on the airglow 
photometer experiment. 26 The airglow photometer was to measure the horizontal and 
temporal characteristics of the nightside thermospheric circulation. That proposal failed 
for reasons external to VOIR, as we shall see. 

The Stanford Center for Radar Astronomy also submitted a proposal; it succeeded. 
Proposing radio and radar experiments on NASA space missions was their normal mode 
of conducting scientific research. Len Tyler, Dick Simpson, and John F. Vesecky proposed 
to study radar backscatter from the surface of Venus, in order to infer the small-scale phys- 
ical texture of the surface, and to relate that texture to the large-scale formations visible 
in the VOIR images. Rather than create a separate investigative group, the Stanford 
researchers proposed that they participate in the radar group with Pettengill. 27 



25. "VOIR, Scientific Investigation and Technical Plan, Proposal to NASA, 2/79," Box 13, JPLMM; 
V-Gramno. 11 (April 1987): 16; V-Gramno. 13 (October 1987): 14; and V-Gramno. 11 (April 1987): 11. 

26. 'VOIR, A Proposal to NASA, Submitted by University of Arkansas, 7/79;" "VOIR, Contract Request 
for Proposal (APE) Airglow Photometer Experiment, 5/81, 12/81;" and "VOIR, Proposal to NASA, for Airglow 
Photometer Experiment for the VOIR Mission," Box 13, JPLMM. 

27. 'VOIR, Proposal to the NASA Management Section, 2/79," Box 13, JPLMM. 



MAGELLAN 187 



The Venus Radar Mapper 

Congress already had voted VOIR a new start in the NASA budget, when Ronald 
Reagan became president in January 1981. As a result of decisions reached in the early 
months of the new administration, the problems foreseen in 1978 overlap with Galileo, 
complication of DSN scheduling, escalated costs, and an opportunity for the Soviet Union 
to obtain Venus SAR images before the United States all came true. National politics 
now took its turn in shaping the VOIR mission. Early in the new Republican administra- 
tion, as a political signal that the new president was serious about cutting the budget, or 
at least the civilian portion of the budget, the budget czar David Stockman pressured 
NASA to sacrifice a major project. NASA chose VOIR. 28 

Failure to fund the project until fiscal 1984, when VOIR became a new NASA start, 
led to a postponement of the launch schedule to April 1988. This postponement provid- 
ed the Soviet Union an opportunity to obtain the first SAR images of Venus. In this case, 
the Cold War rhetoric of the White House did not have its equivalent in the Space Race. 
The Space Race was dead. Starting in the early 1970s, as the United States withdrew from 
the war in Vietnam and the Apollo program's objective had been met several times over, 
a period of detente started. The U.S. and U.S.S.R. signed an accord in 1972 to allow the 
exchange of scholars between the two countries. A decade later, however, the United 
States let the accord lapse in protest over the Soviet imposition of martial law in Poland. 
Nonetheless, many U.S. and Soviet scientists sought to collaborate, not compete, and they 
did so with the tacit approval of their governments. Cold War rivalry and competition no 
longer held sway. 29 

The justification for canceling VOIR was its high cost. The project, conflated into an 
exploration of the surface, interior, atmosphere, and ionosphere of Venus, carried a total 
price tag of $680 million. NASA andJPL sought ways to slash that price tag to $200 to $300 
million. 30 In the opinion of Gordon Pettengill, the project "was climbing a cliff. The pro- 
ject people at NASA Headquarters were told that if they could cut the cost in half, they 
could have their project. In other words, they had to do it for $300 million instead of $600 
million. So an ad hoc group of JPL and NASA Headquarters people was put together to 
study ways of cutting costs." 31 

NASA renamed the low-cost reduced mission the Venus Radar Mapper (VRM) , 32 The 
trick was to lower the price tag, while still getting the science done. A number of 
approaches were suggested and taken, not all of which were technological, such as the 
reduction of personnel levels. Many of the cost-cutting decisions directly reduced the 
scientific scope of the mission. For example, one of the earliest decisions was to jettison 
all scientific experiments that did not use the radar. Only the altimetry and imaging 
experiments, which used the radar instrument, and the gravity experiment, which was car- 
ried out by the Deep Space Network, remained. Among the rejected experiments was the 
airglow photometer. 33 As Pettengill pointed out, however, "they saved $150 million by 



28. Pettengill 28 September 1993; Saunders, Pettengill, Arvidson, William L. Sjogren, William T. K. 
Johnson, and L. Fieri, "The Magellan Venus Radar Mapping Mission," Journal of Geophysical Research vol. 95, no. 
B6 (1990): 8339; Waff, Jovian Odyssey: A History of NASA's Project Galileo, chapter "Surviving the Reagan 
Revolution," pp. 8-10, Waff materials. 

29. Henry S. F. Cooper, Jr., "A Reporter at Large: Explorers," The New Yorker 64 (7 March 1988): 50. 

30. "VOIR, Venus Mapper New Start Plans, 3/82," and "VOIR, Venus Radar Mapper, A Proposed 
Planetary Program for 1988," Box 10, JPLMM. 

31. Pettengill 28 September 1993. 

32. For a brief period in 1981 and 1982, project documents used the name Venus Mapping Mission 
(VMM). 

33. "VOIR, Project Management, Venus Orbiting Imaging Radar, 1981-82," Box 14; "VOIR, Venus 
Mapper Briefing to NASA Headquarters, 1/82," Box 10; and "VOIR, Request for Proposal for VOIR Synthetic 
Aperture Radar, 7/81, 3/3," Box 13, JPLMM. 



1 88 TO SEE THE UNSEEN 



getting rid of the four non-radar experiments that originally were intended for the 
mission." 34 

Throughout various iterations of the project, the dimensions of the high and low res- 
olution radar images vacillated. In fact, for a while, the high resolution detailed images of 
selected surface features disappeared entirely. In an early 1981 iteration, the VRM was to 
map at least 70 percent of Venus with a resolution of 600 meters and take high resolution 
(150-meter) data over about one percent of the planet. As described at a January 1982 
briefing at NASA Headquarters, however, the VRM was to have no high resolution capa- 
bility and would image only 70 percent of the planet with a resolution of better than one 
km. At a February 1982 conference held at JPL for the selected contractors, Hughes 
(SAR) and Martin Marietta (spacecraft), the SAR performance parameters called for cov- 
erage of 90 percent of the planet with a single resolution of 300 meters. By 1984, though, 
when the VRM became a NASA new start, the baseline performance had been raised to 
resolutions of 215 meters by 150 meters and 480 meters by 250 meters. 35 

The resolution, and consequently the science that the VRM would achieve, was a 
trade-off against the cost of the project. Only by lowering overall costs did JPL and NASA 
manage to put together a mission capable of high resolution. One of the key cost-reduc- 
tion approaches was to "maximize inheritance," a term that meant to borrow as much 
technology from other projects as possible. Magellan was to be pieced together from other 
NASA projects. 

Among the projects from which the VRM borrowed, or considered borrowing, were 
Viking, Voyager, Galileo, and ISPM (International Solar Polar Mission). The VRM pro- 
posed borrowing such hardware items as the Voyager 3.7-meter dish antenna for its syn- 
thetic aperture radar, Galileo's tape recorder, and Viking's S-band low-gain antenna. Also, 
JPL suggested using NASA standard equipment as well as various SEASAT parts, such as 
sun sensor and solar array drive electronics and the solar array actuators. 36 

In order to improve the VRM's data handling capabilities, JPL modified the radar 
guidelines in order to use the Galileo Golay code, rather than the Golay code planned by 
Hughes (contractor for the SAR) . The Galileo Golay code and a restructuring of the radar 
burst header format (for more efficient handling by the Deep Space Network) resulted in 
a considerable saving in ground software costs. 

Another key decision was the switch from a circular to an elliptical orbit. With an 
elliptical orbit, the parameters of the radar varied as a function of the spacecraft's altitude 
above the planet's surface. Mapping from an elliptical orbit eliminated the need for aer- 
obraking. Aerobraking is a technique for trimming a spacecraft's orbit by having it pass 
repeatedly through a planetary atmosphere. Its use would reduce the amount of propul- 
sion needed for initial orbit insertion. Aerobraking offered a low-cost, low-risk option that 
would both save fuel, and therefore mission weight, and lower mission costs. 37 

Using digital processing to simplify the electronics was a significant saver of money. 
Original VOIR planning centered on analog processing for the radar, but by 1981 it had 
become clear that using digital circuitry was the preferred technology. The parameters of 
an analog system could not change during flight; so, aerobraking and a circular orbit were 
necessities. Digital processing allowed the radar parameters to change during flight, there- 
by tolerating the variations of a less expensive elliptical orbit. 38 



34. Pettengill 28 September 1993. 

35. "VOIR, Request for Proposal for VOIR Synthetic Aperture Radar, 7/81, 3/3," Box 13; "VOIR, Venus 
Mapper Briefing to NASA Headquarters, 1/82," Box 10; "VOIR, Venus Mapper Conference w/Hughes and 
MMC, 2/82," Box 10; and "VOIR, Project Management Report, 1984, 1/2," Box 14, JPLMM. 

36. 'VOIR, Venus Mapper Briefing to NASA Headquarters, 1/82," Box 10; "VOIR, Venus Mapper New 
Start Plans, 3/82," Box 10; and "VOIR, Venus Radar Mapper, A Proposed Planetary Program for 1988," Box 10, 
JPLMM. 

37. "VOIR, Project Management Report, 1984, 1/2," Box 14, JPLMM. 

38. Pettengill 28 September 1993. 



MAGELLAN 



189 



The Microsymposia 



The decisions to change the orbital geometry, use digital processing, and borrow 
technology from other projects lowered project costs to the point where VRM became a 
new NASA start in 1984. As a result of the postponed launch of VRM, Soviet scientists 
gained an important scientific opportunity to image Venus. When it appeared that the 
United States would launch VOIR on schedule, Soviet scientists decided to launch their 
own Venus imaging mission only if the United States did not send a Venus radar mapper 
before 1984. Once NASA delayed launch of the VRM beyond 1984, Soviet scientists had 
to move forward their own Venus radar mapper very quickly in order to seize the oppor- 
tunity. 

In June 1983, the Soviet Union flew two spacecraft equipped with radar mappers to 
Venus; they arrived four months later. Venera 15 and 16 covered the same polar region of 
Venus (30 North to the pole), probably on the assumption that one of the spacecraft 
might fail. Their goal was to map that region at a resolution of one to two km in daily, 150 
by 7,000 km strips 10 to the side of the orbital track, covering a total area of 115 million 
square kilometers by the time the main mission ended in July 1984. 39 




fOTOKrtPTft. 



J1MCT : 



Figure 31 

Radar image of Venus, near Maxwell Monies, made by Venera 15 and 16. (Courtesy of NASA, photo no. 88-H-8.) 



39. Andrew Wilson, Solar System Log (London: Jane's, 1987), pp. 112-113. 



190 TO SEE THE UNSEEN 



Interpreting the images from the Venera 15 and 16 mission required more informa- 
tion about Venus surface features than the Soviet Union had available. Previous Soviet 
missions had landed only in limited areas of the planet. Soviet scientists, desperately in 
need of information, turned to their American colleagues to exchange Venus data. 

Since the Apollo era, several American scientists had made frequent trips to Moscow 
and to international meetings where they met Soviet planetary scientists. Of those 
American scientists, two of the most important ones for the Magellan mission were Jim 
Head of Brown University and Hal Masursky (USGS), a member of the Pioneer Venus sci- 
ence team. As Venera 15 and 16 data became available, its value to future American explo- 
ration of Venus, especially the VRM mission, was apparent, and a parallel American inter- 
est in collaboration developed. 

On 25 March 1984, Alexander Basilevsky, a geologist and chief of the Vernadsky 
Institute Planetology Laboratory, and Valery L. Barsukov, director of the Vernadsky 
Institute (the Soviet equivalent of the USGS), presented Venera 15 and 16 results at the 
Lunar and Planetary Science Conference held in Houston. United States scientists appre- 
ciated that the Venera 15 and 16 SARs had yielded mosaickable images of a large part of 
the northern hemisphere. 

COMPLEX, the Committee on Planetary and Lunar Exploration of the Space 
Science Board, requested that VRM scientists present an assessment of the Venera 15 and 
16 accomplishments, as well as a summary of VRM capabilities and, if deemed desirable, 
ways of improving VRM. Gordon Pettengill presented what was known about the Soviet 
Venera mission, including SAR characteristics, range of resolution, and coverage, and he 
compared Venera results with Arecibo high resolution range-Doppler images. Having reli- 
able images of Venus was vital to the planning of the VRM mission. Although VRM scien- 
tists already had data with which to plan the mission, the Venera 15 and 16 data would 
have added important information on the northern hemisphere. Only two other sources 
of images of Cytherean surface features were available. 

One source was Pioneer Venus. Its radar altimeter measured the height of about 
90 percent of the surface at roughly 75 km intervals, while the mapper mode furnished 
low (20 to 40 km) resolution radar images of only the equatorial region. Pioneer Venus 
had not covered the northern polar region, unlike Venera 15 and 16. Higher resolution 
imaging was available from Arecibo, the second source of Venus surface images. 40 Arecibo 
covered about 25 to 30 percent of the planet at resolutions around 2 to 4 km. However, 
Arecibo could image well only the hemisphere of Venus facing Earth at inferior conjunc- 
tion. 41 

If they could be had on magnetic tape in a digital format, the Venera 15 and 16 data 
would have assisted VRM planning significantly. The data did become available, but not 
through any political maneuvering by the corresponding state departments or other high- 
level official channels. The exchange of scientific results between Soviet and U.S. scien- 
tists interested in the surface features of Venus came about as the result of an arrangement 
made among the scientists themselves and their parent institutions. 

The 1 1 March 1985 session on Venus at the Lunar and Planetary Science Conference 
featured Soviet presentations of their recent interpretations of Venera 15 and 16 results 
by Alexander Basilevsky, Valery L. Barsukov, and two others from the Vernadsky Institute. 
Subsequently, on 19-20 March 1985, the first microsymposium took place at Brown 
University. The four Soviet scientists reviewed recent results of Venera 15 and 16, Arecibo, 
Pioneer Venus, as well as future Venus missions and Venus science in general. Among 
those attending were geologists James Head and Harold Masursky and radar astronomers 
Gordon Pettengill and Don Campbell of Arecibo. 



40. "VOIR, Project Management Report, 1984, 1/2," Box 14, JPLMM. 

41. Campbell 8 December 1993. 



MAGELLAN 191 



It was at the March 1985 microsymposium that James Head reported that the Soviets 
appeared to be receptive to the idea of providing some of their data. Preliminary results 
indicated that the Venera SAR radar parameters would not be a major obstacle to their 
use by American scientists. Moreover, both Soviet and American investigators had reached 
a preliminary agreement on the choice of a particular small feature for the definition of 
the Venus prime meridian. The features had appeared in both the Arecibo range-Doppler 
images and the Venera 15 and 16 SAR images. Establishment of a coordinate system was 
important to the planned VRM cartography efforts. 

In November 1985, Vladimir Kotelnikov, the leader of Soviet ground-based radar 
astronomy research, then head of Interkosmos, delivered to Jim Head a tape with one 
strip of digital Venera image data with accompanying altimetry. Head distributed the tape 
to Saunders, Pettengill, Campbell, and Masursky for analysis. They had no difficulty in dis- 
playing the image using conventional American image processing techniques. 

The Soviet-American agreement to exchange Venus data was underway. The agree- 
ment materialized as a protocol signed in 1982 between the Governor of Rhode Island 
(the location of Brown University) and the Soviet Academy of Sciences. Under the agree- 
ment, one microsymposium per year was to take place in each country. Traditionally, the 
American microsymposium has been held in March or April at Brown University; while 
the Soviet meeting takes place at the Vernadsky Institute in Moscow in August. James 
Head organized the Brown University group, and Valery Barsukov, director of the 
Vernadsky Institute, organized the Soviet group. The creation of the microsymposia owed 
much to the fact that Head was a guest investigator on Venera 15 and 16. 42 

The Soviet data delivered over the following years at subsequent microsymposia 
played an important role in the creation of planning maps for the VRM/Magellan mis- 
sion. The microsymposia were but one forum within which geology and radar communi- 
ties worked together. The VRM Radar Investigation Group (in charge of the radar sci- 
ence) was another forum that brought the two communities together in a common effort. 
The Radar Investigation Group (RADIG) was a large and multifaceted organization typi- 
cal of Big Science. In order to more effectively coordinate and carry out VRM and 
Magellan science, Pettengill divided the group into smaller subgroups (Table 6). 

The VRM (and later Magellan) Radar Investigation Group combined the former 
Synthetic Aperture Radar Group and the Altimetry Investigation Group of the VOIR pro- 
ject. Gordon Pettengill headed the Radar Investigation Group (RADIG). Three RADIG 
subgroups dealt with mission design, while three other subgroups concerned themselves 
with scientific interpretation. These last three subgroups treated cartography and geodesy, 
surface electrical properties, and geology and geophysics. Geology and geophysics, the 
largest and most complex area of scientific interpretation, consisted of even smaller 
groups dealing with volcanic and tectonic processes; impact processes; erosional, deposi- 
tional, and chemical processes; and isostatic and convective processes. 43 

Not only did the RADIG bring together planetary radar and geology communities, 
but it illustrated how space flight science groups organized Little Science to function as 
Big Science, if only on a temporary basis within ephemeral organizations. Ordinarily, in a 
way characteristic of Little Science, scientists work alone at a university or technical school 
with a small budget and modest laboratory equipment. NASA space missions bring these 
individual scientists together and make them function in ways customarily associated with 
Big Science, mainly as part of a large group. Any given scientist works as a member of two 
groups, one defined by a flight instrument and the other by the scientist's discipline or 



42. Cooper, "A Reporter," p. 50; Ford 3 October 1994; Campbell 8 December 1993; "VOIR, Report 
Project Management, 1985," Box 14, JPLMM. The August 1991 microsymposium was delayed until November 
because of the putsch. 

43. V-Gram no. 8 (24 March 1986) : 2-4. 



192 



TO SEE THE UNSEEN 





Table 6 
Members of Magellan Radar Investigation Group (RADIG) 




Scientist 


Institution 




Raymond E. Arvidson 
Victor R. Baker 


Washington University 
University of Arizona 






Joseph H. Binsack 
Donald B. Campbell 


MIT 
NAIC, Cornell 






Merton E. Davies 


Rand Corporation 






Charles Elachi 


JPL 






John E. Guest 


University of London 






James W. Head, III 


Brown University 






William M. Kaula 


UCLA 






Kurt L. Lambeck 


Australian National University 






Franz W. Leberl 


Independent Consultant 






Harold C. MacDonald 


University of Arkansas 






Harold Masursky 


US Geological Survey 






Daniel P. McKenzie 
Barry E. Parsons 


Cambridge University 
Oxford University 






Gordon H. Pettengill 


MIT 






Roger J. Phillips 
R. Keith Raney 


Southern Methodist University 
Canada Center for Remote Sensing 






R. Stephen Saunders 


JPL 






Gerald G. Schaber 


US Geological Survey 






Gerald S. Schubert 


UCLA 






Laurence A. Soderblum 


US Geological Survey 






Sean C. Solomon 


MIT 






H. Ray Stanley 


NASA, Wallops Island 






Manik Taiwan! 


Gulf Research and Development 






G. Leonard Tyler 


Stanford University 






John A. Wood 


Harvard-Smithsonian Astrophysical 








Observatory 







subdiscipline. Grouped together around a common instrument, scientists jointly design 
the instrument that will generate their data. Grouped together around a common scien- 
tific interest, such as magnetospheres or geology, scientists jointly utilize data derived from 
the operation of all flight instruments. However much these scientists function within a 
Big Science organization, the organization itself is defined by the temporary lifetime of 
the project. In the end, they are once more Little Science. 

Osmosis 

In December 1985, NASA Headquarters notified JPL that the VRM had a new name, 
Magellan. The name reflected NASA's general plan of naming major planetary missions 
after famous scientists and explorers (Galileo, Magellan, Cassini). 44 Ferdinand Magellan 
had been a Portuguese navigator and explorer who led an expedition into the Pacific 
Ocean under the Spanish flag. 

By the end of 1985, construction of the Magellan radar instrument was underway. 
After Hughes Aircraft Company and Goodyear Aerospace Corporation completed Phase 
B studies of the project in June 1980, JPL issued a Request for Proposals for the synthetic 
aperture radar system, including the antenna design, in April 1981. The selection of the 
SAR and spacecraft contractors were separate processes. 45 



44. "VOIR, Report Project Management, 1985," Box 14, JPLMM. 

45. "VOIR, Venus Orbiting Imaging Radar Review, 4/80," Box 10, and "VOIR, Request for Proposal for 
VOIR Synthetic Aperture Radar, 7/81, 1/3," Box 13, JPLMM. 



MAGELLAN 193 



Hughes had hoped to turn its experience with the Pioneer Venus orbiter mapper 
into an advantage, while Goodyear had been one of the first firms to commercialize air- 
craft SAR systems to study the Earth. In 1983, NASA and JPL signed contracts with Hughes 
and Martin Marietta for the SAR and spacecraft. Hughes signed the definitive radar con- 
tract on 24 January 1984, and the contract was executed 27 January 1984. Throughout 
1985 and 1986, Hughes increased the number of employees working on the Magellan 
radar. The project had the second highest priority within the Hughes Space and 
Communication Group, behind a smaller classified project. 46 Hughes' Pioneer Venus 
gambit had paid off. 

Magellan was on schedule and under budget when the Space Shuttle Challenger blew 
up on 28 January 198&. The tragedy caused a serious delay in the Magellan launch sched- 
ule. In fact, the disaster adversely affected all Shuttle flights. The Shuttle would not fly 
until the cause of the Challenger accident was determined and corrective solutions found 
to prevent future repetitions of the accident. Only then would a new Shuttle flight sched- 
ule be drawn up. 

In February 1986, Magellan mission personnel began to appraise probable launch 
dates. Realizing the uncertainties of the Shuttle launch schedule, they investigated two 
launch windows that followed the approved launch period in April 1988. One was between 
28 October and 16 November 1989, the other between 25 May and ISJune 1991. In each 
case, Magellan would spend eight months in orbit performing its prime mission, and the 
mission would end at superior conjunction, in November 1990 or in June 1992, depend- 
ing on the launch window. 47 

A delayed launch also raised the likelihood of conflicts with the Galileo launch. If 
Magellan held to its approved launch schedule in April 1988, and Galileo delayed 13 
months, then coverage conflicts on the Deep Space Network eased considerably. 
Whatever launch window Magellan eventually had, conflict with the Galileo launch and 
scheduling of the Deep Space Network would have to be taken into consideration. 
Further complicating the launch schedule was the cancellation in June 1986 of the 
Shuttle/Centaur, which was to launch Magellan. After a study of alternate launch vehicles, 
in October 1986 NASA settled on a combination of the Shuttle and a launcher known as 
an Inertial Upper Stage (IUS) and assigned Magellan a position on the Shuttle manifest 
for April 1989. 48 

The change required reduction of the spacecraft mass, as well as new structural loads 
analyses. In order to undertake the analyses, a second spacecraft structure was needed for 
static load tests. The only one available was on the Voyager spacecraft hanging in the 
Smithsonian Air and Space Museum in Washington. NASA made arrangements to borrow 
the Voyager bus from the museum and conducted the tests. 49 

The Challenger accident also affected Magellan's use of Galileo technology. Because 
Magellan launched before Galileo, the extra Galileo components were not available. 
Ground support equipment to be borrowed from Galileo were unavailable. Now the 
"spare parts" Magellan was to borrow from Galileo had to be returned to Galileo and pur- 
chased new for Magellan. 

The delay of Magellan also raised the cost of the project. The total dollar impact, 
including the cost of hardware, mission design, and mission operations, was estimated to 
be about $150 million. Gordon Pettengill summed up the situation: 'That disaster need 
not have happened, but it did; it was just one of those things. Magellan would not have 
been as expensive, if we had launched when we were originally planned to launch." 50 



46. Various documents, Box 6, and "VOIR, Report Project Management, 1986, 1/2," Box 14, JPLMM. 

47. "VOIR, Report Project Management, 1986, 1/2," Box 14, JPLMM. 

48. V-Gram no. 10 (January 1987): 1 and 4. 

49. V-Gram no. 10 (January 1987): 1. 

50. Pettengill 28 September 1993; V-Gram no. 10 (January 1987): 1. 



194 TO SEE THE UNSEEN 



JPL received unofficial notification in May 1986 from NASA Headquarters that 
Magellan had slipped to the October-November 1989 launch window, but no official 
launch date had yet been established. Nonetheless, the Magellan project proceeded on 
the assumption of that launch window. 51 

Meanwhile, the collection and exchange of radar data for the assembling of maps to 
be used in planning the mission proceeded. The Brown University-Vernadsky Institute 
microsymposia continued to play a vital role in the exchange of scientific information 
between American and Soviet scientists. In April 1986, the third international microsym- 
posium on Venus took place at Brown University. Valery Barsukov, Alexander Basilevsky, 
and four other Soviet scientists presented preliminary scientific results of the Venera 15 
and 16 missions and a description of the radar system. 

The Soviet scientists presented the Magellan project with three Venera data tapes 
consisting of unpublished SAR digital data. They stipulated that the data be used strictly 
for planning the Magellan project; it was not for scientific publication or distribution, 
until the Soviet scientists had published the information. The request was reasonable; it 
protected their priority of discovery. In exchange, the Soviet scientists received high reso- 
lution digital data from the Viking mission to assist them in planning their Phobos mis- 
sion to Mars's moon. 52 

The following year, Magellan investigators James Head, Steve Saunders, Hal 
Masursky, Gerald Schaber, and Don Campbell attended a microsymposium held 11 to 15 
August 1986 at the Vernadsky Institute in Moscow. They and their Moscow colleagues 
exchanged views on the interpretation of Venus data from Venera 15 and 16 and Arecibo. 
The Soviet investigators presented the Magellan scientists with eight tapes of Venera 15 
and 16 digital radar images and altimetry profiles for use by the Magellan project for plan- 
ning purposes. 53 

At the following microsymposium held at Brown University in March 1987, scientists 
debated the origin and evolution of volcanic structures and deposits, domes, parquet ter- 
rain, impact craters, ridge and linear mountain belts, and plate tectonics. Only slight con- 
sensus over the interpretation of features emerged, because the resolution of features in 
Pioneer Venus images (25 km) and Venera 15 and 16 images (1-3 km) was sufficiently 
coarse to give rise to ambiguities in interpretation. Magellan's higher global resolution 
(about 300 meters) promised to resolve many questions of geologic interpretation. Soviet 
scientists provided the Magellan project with additional Venera 15 and 16 digital tapes; in 
return they received more high-resolution Viking imaging data of Phobos and the surface 
of Mars. 54 

The microsymposia demonstrated the fruitful cross-fertilization of planetary geology 
and radar. In order to facilitate the use of radar data by geologists, Magellan Project 
Manager John Gerpheide, Program Scientist Joseph Boyce, Principal Investigator Gordon 
Pettengill, Project Scientist Steve Saunders, and Science and Mission Design Manager 
Saterios Sam Dallas formulated preliminary plans in July 1986 for various radar work- 
shops. The first, to be held in 1987, was to cover radar operation and processing, the sec- 
ond the interactions between radar waves and planetary surfaces, and the third interpre- 
tation of SAR images. The second and third workshops were held in 1988 and 1989, 
respectively. The sessions were open to Magellan scientists and to the Planetary Geology 
and Geophysics Program investigators. In addition, they planned one-day Venus science 
symposia to be held in conjunction with other project meetings for each year between 
1987 and 1989. 



51. "VOIR, Report Project Management, 1986, 1/2" and "VOIR, Report Project Management, 1986, 
2/2," Box 14, JPLMM. 

52. "VOIR, Report Project Management, 1986, 1/2," Box 14, JPLMM. 

53. 'VOIR, Report Project Management, 1986, 2/2," Box 14, JPLMM. 

54. V-Gramno. 12 (July 1987): 1. 



MAGELLAN 195 



In 1987, 32 scientists and project personnel participated in the field trip to various 
sites in the Mojave Desert and Death Valley. 55 The goal was to compare a variety of geo- 
logic features with SAR images of the areas. Steve Wall, Magellan Radar Experiment rep- 
resentative, organized the field trip, which Tom G. Farr of JPL's Geology and Planetology 
Section led. Gerald Schaber of the USGS contributed to the technical presentation by 
sharing his knowledge of Death Valley. 56 

In May 1988, the USGS Flagstaff hosted another field trip, which was incorporated 
as part of the quarterly meeting of Magellan scientists and project staff. The major objec- 
tive was to familiarize participants with specific radar geology targets in a semi-arid, rela- 
tively vegetation-free environment. The trip also entailed comparing geologic features 
with X-band and L-band SAR images. The field exercise was planned and led by Gerald 
Schaber, Richard Kozak, and George Billingsley, all three with the USGS Flagstaff. 57 

These field trips helped to introduce geologists to the interpretation of radar data. 
Geologists learn from "hands-on" experience, but that kind of experience is impossible 
when dealing with the geology of Venus. Radar images, moreover, are not created by the 
reflection of light, but by the scattering and reflection of electromagnetic waves. They can- 
not be read like photographs, and radar maps cannot be read like ordinary geological 
maps. 

In order to fill in that gap, data to create a series of S-band radar images of the lunar 
surface were collected at the Arecibo Observatory between 1982 and 1992. The images 
were made at various angles of incidence at a number of known lunar locations, such as 
the Apollo 15 and 17 landing sites, Mare Imbrium, and craters Copernicus and Tycho, in 
order to provide experience in interpreting surface geology in radar images. Don 
Campbell, assisted by Peter Ford of MIT and later by Cornell graduate student Nick Stacy, 
made the observations and images in collaboration with Jim Head of Brown University. 
While initial image resolutions ranged from 200 to 300 meters, Nick Stacy brought image 
resolution down to 25 meters beginning in 1990. Elaborate data processing techniques 
attempted to replicate the synthetic aperture radar techniques used from spacecraft and 
aircraft. 58 

As Gordon Pettengill pointed out, the workshops were not the main path for geolo- 
gists to learn about radar. 'The people who attended those made up a small fraction of 
the overall community. That route is an exception to what I would call the more general 
experience. Generally, people become part of a team, and they work with radar people, 
like myself, who then, by a process I would call osmosis, pass along the mystique of what 
is going on, when you see these structures on a radar image, how to interpret them, and 
what to look out for, so you don't make errors." 

This process of osmosis, Pettengill explained, "is the best way to go. A formal course 
is difficult. They call them workshops. They are useful. But you need both. You need the 
workshop as well as years of working with other people and growing used to what you are 
seeing." 59 

That process of osmosis was most evident at the Arecibo Observatory, where Don 
Campbell and his graduate students Barbara Burns and Nick Stacy and Research Associate 
John K. Harmon, collaborated with Jim Head and other geologists at Brown University 
through an informal accord between the NAIC and Brown University beginning around 
1980. The heart of the accord was a cooperative effort to analyze Arecibo Venus imagery. 



55. "VOIR, Report Project Management, 1986, 2/2," Box 14, JPLMM. 

56. V-Gramno. 11 (April 1987): 1. 

57. V-Gmm no. 15 (January 1989): 15. 

58. Ford 3 October 1994; Campbell 8 December 1993; Nicholas John Sholto Stacy, "High-Resolution 
Synthetic Aperture Radar Observations of the Moon," Ph.D. diss, Cornell University, May 1993; NAIC QR 
Ql/1982, Q4/1986, Q2/1990, Q4/1990, and Q3/1992. 

59. Pettengill 29 September 1993. 



196 TO SEE THE UNSEEN 



As a result of the arrangement, a number of Brown students, such as Richard W. Vorder 
Brueggie and David A. Senske, became involved in the analysis of Arecibo radar range- 
Doppler imagery and wrote their theses from the data. 

'The effort was not under any formal agreement between the NAIC and Brown 
University," Don Campbell explained. "We badly needed the backing of a planetary geol- 
ogy group. We were into geology at this point. We were down to a few kilometers of reso- 
lution, and they were extremely enthusiastic. Jim Head was very enthusiastic and had a lot 
of students. They were very intent on getting ready for the Magellan mission and spent a 
lot of effort on both the Pioneer Venus and Venera data sets." 60 

The Arecibo-Brown arrangement thus fostered the geological interpretation of 
Venus radar images well before Magellan began its mapping mission. A major area of 
interest was in identifying and explaining tectonic activity on the planet. Some of the 1979 
high-resolution Arecibo radar images suggested Earth-like tectonic features, such as folds 
and faults, while 1983 Arecibo radar images confirmed the presence of rifting in the 
southern Ishtar Terra and surrounding plains and general tectonic activity in Maxwell 
Monies. 61 Later studies examined evidence for tectonic activity in Beta Regio, Guinevere 
Planitia, Sedna Planitia, and western Eistla Regio in the planet's equatorial region, as well 
as in the southern latitudes around Themis Regio, Lavinia Planitia, Alpha Regio, and Lada 
Terra. fi 2 

Don Campbell also collaborated with Jim Head's group in searching for evidence of 
volcanism. Arecibo radar images of southern Ishtar Terra and the surrounding plains 
revealed significant details of volcanic activity. Images made from data gathered at Arecibo 
during the summer of 1988 of the area extending from Beta Regio to the western Eistla 
Regio furnished strong evidence that the mountains in Beta and Eistla Regiones, as well 
as the plains in and adjacent to Guinevere Planitia, were of volcanic origin. Arecibo radar 
images of the southern latitudes showed additional evidence for past volcanic activity on 
Venus. 63 

The study of cratering on Venus started by Barbara Burns for her doctoral thesis con- 
tinued at Arecibo, too. She based her initial analysis on data collected in 1977 and 1979. 
As of 1985, Burns was able to identify only two features that exhibited unambiguous radar 
characteristics that could tentatively distinguish them as either volcanic (Colette) or 
impact (Meitner) in origin. Don Campbell, with Jim Head and John Harmon, continued 



60. Campbell 8 December 1993. 

61. Campbell, Head, John K. Harmon, and Alice A. Hine, "Venus: Identification of Banded Terrain in 
the Mountains of Ishtar Terra," Science 221 (1983): 644-647; L. S. Grumpier, Head, and Campbell, "Orogenic 
Belts on Venus," Geology 14 (1986): 1031-1034; Stofan, Head, and Campbell, "Geology of the Southern Ishtar 
Terra/ Guinevere and Sedna Planitae Region on Venus," Earth, Moon, and Planets 38 (1987): 183-207; R. W. 
Vorder Brueggie, Head, and Campbell, "Orogeny and Large-Scale Strike-Slip Faulting on Venus: Tectonic 
Evolution of Maxwell Monies," Journal of Geophysical Research vol. 95, no. B6 (1990): 8357-8381. 

62. David A. Senske, Campbell, Stofan, Paul C. Fisher, Head, Stacy, J. C. Aubele, Hine, and Harmon, 
"Geology and Tectonics of Beta Regio, Guinevere Planitia, Sedna Planitia, and Western Eistla Regio, Venus: 
Results from Arecibo Image Data," Earth, Moon, and Planets 55 (1991): 163-214; Bruce A. Campbell and 
Campbell, "Western Eistla Regio, Venus: Radar Properties of Volcanic Deposits," Geophysical Research Letters 
vol. 17, no. 9 (1990): 1353-1356; Senske, Campbell, Head, Fisher, Hine, A. de Charon, S. L. Frank, S. T. Keddie, 
K. M. Roberts, Stofan, Aubele, Grumpier, and Stacy, "Geology and Tectonics of the Themis Regio-Lavinia 
Planitia-Alpha Regio-Lada Terra Area, Venus: Results from Arecibo Image Data," Earth, Moon, and Planets 55 
(1991): 97-161. 

63. Stofan, Head, and Campbell, "Geology of the Southern Ishtar Terra/Guinevere and Sedna Planitae 
Region on Venus," Earth, Moon, and Planets 38 (1987): 183-207; Campbell, Head, Harmon, and Hine, "Venus: 
Volcanism and Rift Formation in Beta Regio," Science 226 (1984): 167-170; Campbell, Head, Hine, Harmon, 
Senske, and Fisher, "Styles of Volcanism on Venus: New Arecibo High Resolution Radar Data," Sein<* 246 (1989): 
373-377; Campbell, Senske, Head, Hine, and Fisher, "Venus Southern Hemisphere: Geologic Character and Age 
of Terrains in the Themis-Alpha-Lada Region," Science 251 (1991): 180-183; Senske, Campbell, Head, Fisher, 
Hine, de Charon, S. L. Frank, S. T. Keddie, K. M. Roberts, Stofan, Aubele, Grumpier, and Stacy, "Geology and 
Tectonics of the Themis Regio-Lavinia Planitia-Alpha Regio-Lada Terra Area, Venus: Results from Arecibo Image 
Data," Earth, Moon, and Planets 55 (1991): 97-161. 



MAGELLAN 197 



Burns's crater studies. Images made from the data collected during the inferior conjunc- 
tion of 1988 of the area from Beta Regio to western Eistla Regio revealed a low density of 
impact craters greater than 15 km in diameter in that region compared to the average 
density for the higher northern latitudes. These crater densities suggested that the plains 
were geologically younger than the northern regions. 64 

Campbell, with graduate student Nick Stacy and computer software manager and 
part-time radar astronomer Alice Hine, made a further analysis of cratering by looking at 
diameter-frequency distributions in the low northern latitudes and the southern hemi- 
sphere. The Arecibo investigators found that the average crater density for all craters in 
the northernmost quarter, using Venera 15 and 16 data, was 1.27 per million square kilo- 
meters, while the average for the southern hemisphere (as imaged by the Arecibo radar) 
was 0.95 per million square kilometers. The different crater densities suggested that the 
southern latitudes were geologically younger than the low northern latitudes imaged by 
Venera 15 and 16. 65 

Don Campbell also participated in the microsymposia organized by Brown University 
and the Vernadsky Institute. As a result, he also came to collaborate with Alexander 
Basilevsky and other Soviet geologists on the interpretation of Venera 15 and 16 results, 
and that collaboration led to co-authorship of a paper with combined Vernadsky Institute 
and Brown University authors. 66 

Don Campbell's osmotic infiltration of the scientific community interested in Venus 
typified the shifting paradigm of ground-based planetary radar astronomy toward geolo- 
gy. Further facilitating that shift was the availability of techniques, hardware, and software 
at Arecibo that yielded high-resolution range-Doppler images and topographical data. 
Image resolution improved to one to three km in 1983 and to 1.5 km in 1988, the last 
observations made before the arrival of Magellan at Venus. 

Because Magellan used a frequency close to that of the Arecibo radar, there was some 
concern that the Arecibo radar might contaminate the Magellan data or endanger the 
spacecraft, so Don Campbell did not pursue Venus mapping after 1988. 67 Nonetheless, the 
participation of Arecibo ground-based investigators in Venus radar geology illustrated that 
the marriage of radar and geology was not limited to Magellan and space-based radars. 



64. Burns and Campbell, "Radar Evidence for Cratering on Venus," Journal of Geophysical Research vol. 90, 
no. B4 (1985): 3037-3047; Campbell, Head, Hine, Harmon, Senske, and Fisher, "Styles of Volcanism on Venus: 
New Arecibo High Resolution Radar Data," Science 246 (1989): 373-377. 

65. Campbell, Stacy, and Hine, "Venus: Crater Distributions at Low Northern Latitudes and in the 
Southern Hemisphere from New Arecibo Observations," Geophysical Research Letters vol. 17, no. 9 (1990): 
1389-1392. 

66. A. T. Basilevsky, B. A. Ivanov, G. A. Burba, L. M. Chernaya, V. P. Kryuchkov, O. V. Nikolaeva, 
Campbell, and L. B. Ronca, "Impact Craters on Venus: A Continuation of the Analysis of Data from the Venera 
15 and 16 Spacecraft," Journal of Geophysical Research vol. 92, no. B12 (1987): 12,869-12,901; Stofan, Head, 
Campbell, Zisk, A. F. Bogomolov, Rzhiga, Basilevsky, and N. Armand, "Geology of a Rift Zone on Venus: Beta 
Regio and Devana Chasma," Geological Society of America Bulletin 101 (1989): 143-156. 

67. Campbell 8 December 1993; Burns, "Cratering Analysis of the Surface of Venus," p. 1; Stofan, Head, 
and Campbell, "Geology of the Southern Ishtar Terra/Guinevere and Sedna Planitae Region on Venus," Earth, 
Moon, and Planets 38 (1987): 183-207; Richard W. Vorder Brueggie, Head, and Campbell, "Orogeny and Large- 
Scale Strike-Slip Faulting on Venus: Tectonic Evolution of Maxwell Montes," Journal of Geophysical Research vol. 95, 
no. B6( 1990) =8357-8381. 



198 



TO SEE THE UNSEEN 




Figure 32 

Radar image of the central portion of Alpha Regio, Venus, at a resolution of about 1.5 km, 1988. This, and the image in 
Fig. 33, illustrate the fine resolutions achieved by the ground-based Arecibo Observatory radar as Magellan began imaging 
Venus. (Courtesy of National Astronomy and Ionosphere Center, which is operated by Cornell University under contract with 
the National Science Foundation.) 



MAGELLAN 



199 




Figure 33 

Radar image of Theia Mons in Beta Regio, Venus, at a resolution of 2 km made from data gathered with the Arecibo 
Observatory radar, 1988. (Courtesy of National Astronomy and Ionosphere Center, which is operated by Cornell University 
under contract with the National Science Foundation.) 



Magellan 



Throughout 1987 and into 1988, assembly of the Magellan spacecraft and final test- 
ing of the radar proceeded. Hardware, testing, and integration costs, coupled with an 
overall tight NASA budget, necessitated cutbacks and deferrals from Magellan's fiscal 
1988 budget to later years. Some of the top staff transferred to other projects. Magellan 
Science Manager Neil Nickle, for instance, stepped down, and Thomas Thompson 
replaced him. Thompson had carried out lunar radar research at Arecibo and Haystack 
as early as the 1960s, and he was still making lunar observations with the Arecibo UHF 
radar as late as 1987. Also, he had been on the SEASAT radar team in the 1970s and more 
recendy had made radar observations of Mars with the Goldstone Mars Station. 68 



68. Thompson 29 November 1994; V-Gram no. 15 (January 1989): 16; V-Gram no. 14 (May 1988): 2; 
NAICQR, Q2/1987. 



200 TO SEE THE UNSEEN 



In September 1988, a month ahead of schedule, the completed craft was shipped to 
Kennedy Space Center, where final assembly and testing took place. The Magellan launch 
date was moved up on the Shutde manifest from October-November 1989 to April-May 
1989 to accommodate the launch of Galileo, which needed to go to Venus for a gravity 
boost. The next launch window, June 1991, would have brought Magellan to Venus near- 
ly a year later than the April-May 1989 opportunity. Launching six months earlier also 
meant that Magellan would have to circle the Sun one and a half times, rather than the 
usual one-half circuit, before encountering Venus. Although this trajectory took Magellan 
almost a year longer to reach Venus than the October-November 1989 opportunity, it still 
saved a year over the June 1991 trajectory. On 4 May 1989, after trouble with software, a 
hydrogen pump, and the weather, the Shuttle Atlantis carried Magellan aloft from 
Kennedy Space Center. Magellan became the first planetary mission launched by the 
Space Shuttle. More problems, including several losses of signal, plagued Magellan's 
mission. 69 

Magellan entered orbit around Venus on 10 August 1990, 15 months after launch. 
On 15 August, the radar sensor was turned on and powered up in preparation for the first 
in-orbit radar test. The next day, during the radar test, the spacecraft lost its "heartbeat" 
and protected itself by invoking on-board fault-protection routines. Ground control noted 
this immediately by the terrifying loss of signal. Communications were re-established, then 
lost a few days later. After a shaky start, the radar began mapping on 15 September 1990. 

Mission personnel arranged the first images into mosaics. The mosaics covered 
about 500 km segments of 30 or more individual image strips. One of the first mosaics was 
centered at 27 South latitude and 339 longitude in the Lavinia region of Venus. It 
showed three large impact craters, with diameters ranging from 37 to 50 km. The craters 
showed many features typical of meteorite impact, including rough, radar-bright ejecta, 
terraced inner walls, and central peaks. Numerous domes of probable volcanic origin 
were visible in the southeastern corner of the mosaic. The domes ranged in diameter 
from 1 to 12 km; some had central pits typical of volcanic shields or cones. 70 

During its 243-day prime mission, Magellan amassed more imaging data than all pre- 
vious U.S. planetary missions combined. 71 Magellan mapped over 90 percent of the plan- 
et's surface, covering regions from 68 South latitude to the North pole. The images were 
to have a resolution of about 120 meters near the equator, degrading slightly to about 190 
meters near the poles because of the elliptical nature of the orbit. Although budgetary 
cuts had threatened to lower the resolution of Magellan radar images, the application of 
advanced digital electronic circuitry had restored the mission's high resolution capability. 

SAR data from each orbit was to be processed to make image strips about 350 pixels 
wide in the across-track dimension by 220,000 pixels in the along-track direction. Some 
1,852 such SAR image strips were to be generated byJPL's Multimission SAR Processing 
Laboratory during the primary mission. These strips were to be sufficient in number and 
coverage to encircle the planet, with overlap of adjacent strips even in lower latitudes. 
Image element widths were 75 meters to properly preserve both the along and cross-track 
spatial resolutions. 

Each strip is called a Full-Resolution Basic Image Data Record or F-BIDR. In total, 
the 1,852 F-BIDR SAR image strips formed a data set in excess of 100 billion bytes. The 
large volume and the unwieldy width-to-length ratios for the data made them unsuitable 
for general use. Thus, further processing was necessary to produce mosaicked images 
(Mosaicked Image Data Records or MIDRs) that could be more readily used in photo- 



69. V-Gram no. 15 (January 1989): 1; V-Gram no. 16 (August 1989): 1. 

70. V-Gram no. 18 (October 1990): 1-2. 

71. V-Gram no. 13 (October 1987): 1. 



MAGELLAN 201 



interpretative studies and in comparisons with the other Magellan data. Generating full- 
resolution mosaics for the 90 percent of the planet covered by F-BIDRs created an enor- 
mous data set, severely taxing available processing facilities. To streamline processing and 
to focus efforts toward production of sets of mosaics that could be used for a variety of 
studies, a decision was made to compile and distribute global mosaics from compressed 
F-BIDR data. 7 2 

The USGS converted the data into a set of 62 maps in the standard 1:5,000,000 USGS 
planetary series. The maps showed SAR data at a resolution of about one km, and they 
were to contain altitude contours. In addition, a set of about 200 photomosaics were to 
show the entire mapped area of the planet at a resolution of 225 meters, and an additional 
set of about 250 photomosaics at the highest resolution, about 100 meters, were to be pre- 
pared for selected sections of the planets. Complementary data products were to include 
a topographic map at about 10-km surface resolution with a height accuracy of better than 
50 meters, as well as special products displaying surface roughness, reflectivity, brightness 
temperature, and emissivity. Today, the radar data is also available in annotated digital 
form on CD-ROMs. 7 3 

Key to creating these and other Venus images was an accurate knowledge of the plan- 
et's pole position and spin vector. An analysis by Irwin Shapiro and John Chandler of 1988 
Arecibo radar data supplied by Don Campbell, Alice Mine, and Nick Stacy provided a new 
pole position, accurate to better than 3 km, and a more accurate measurement of the 
planet's rotational period. 74 Such participation in NASA space missions by radar 
astronomers as "mission support" already had been the norm for two decades. 

Don Campbell and G-ordon Pettengill also worked closely with Stanford scientists 
Len Tyler and Dick Simpson, who participated on the science team. Tyler chaired the 
Surface Electrical Properties (SEP) Team, composed of Tyler, Campbell, and Gerald 
Schaber (USGS). Tyler, Simpson, and John Vesecky used the altimeter function of 
Magellan's radar to look at dielectric constants and roughness, to study the top meter of 
Venus's surface, and to relate its structure to its interaction with radar waves. They trans- 
ferred their data to a CD, with the intention of sending copies to scientists with whom they 



72. V-Gram no. 10 (January 1987): 9-10. 

73. V-Gram no. 8 (24 March 1986) : 2-3. 

74. Magellan Final Science Reports, Report D-11092 (Pasadena: JPL, 22 October 1993), p. 25; Shapiro, 
Chandler, Campbell, Hine, and Stacy, "The Spin Vector of Venus," The Astronomical Journal 100 (1990): 
1363-1368. See also the analysis done at Goldstone: Slade, Zohar, and Jurgens, "Venus: Improved Spin Vector 
from Goldstone Radar Observations," The Astronomical Journal 100 (1990): 1369-1374. 



202 



TO SEE THE UNSEEN 




Figure 34 

Radar image of Venus at 65 degrees east longitude, along the western edge of Maxwell Mantes, made from Magellan observa- 
tions. The sloping edge of Maxwell Mantes, the highest mountain on Venus, is visible along the right hand side of the image. 
The. imaged area is 300 km wide. (Courtesy of NASA, photo no. 90-H-752.) 

collaborated, such as Don Campbell, Peter Ford, and Gordon Pettengill, as well as inter- 
ested geologists. 75 

Typical of Big Science projects, Magellan thus became a meeting ground for differ- 
ent scientific disciplines and subdisciplines. Its broad tent covered traditional ground- 
based radar astronomy and Stanford bistatic radar astronomy, as well as planetary geolo- 
gy. Magellan accelerated cross-fertilization between planetary geology and radar that 



75. Simpson 10 May 1994; Simpson and Tyler, "Venus Surface Properties from Magellan Radio and 
Radar Data," V-Gram 18 (October 1990): 12-18. For the results, see Tyler, Ford, Campbell, Charles Elachi, 
Pettengill, and Simpson, "Magellan: Electrical and Physical Properties of Venus' Surface," Science 252 (1991): 
265-270; Tyler, Simpson, Michael J. Maurer, and Edgar Holmann, "Scattering Properties of the Venusian 
Surface: Preliminary Results from Magellan, " Journal of Geophysical Research 97 (1992): 13,115-13,139. Pettengill 
and Ford also produced dielectric-constant and roughness maps to accompany the global topography and emis- 
sivity data they produced. The Stanford investigators used different, but complementary, algorithms that com- 
bined the altimetry and imaging SAR data to obtain estimates of surface roughness and dielectric constant. Both 
data sets were made available on CD- ROMs. 



MAGELLAN 203 



made radar results (mainly range-Doppler images and topography) more accessible to a 
larger community of investigators. As Don Campbell reflected: "We are suddenly much 
more respectable than we used to be! I don't want to characterize what people thought of 
us, but to some degree I suspect that we were regarded as a litde bit of the fringe. Radar 
astronomy was regarded as a messy and expensive occupation. We came up with good 
stuff, but how we did it was not all clear!" 76 

As radar astronomers grew closer to planetary geology, they sought out their new 
audience in new scientific settings. Radar astronomers still discussed their findings at 
meetings of the IAU, the AAS Division for Planetary Science, and URSI, but also at 
American Geophysical Union (AGU) meetings. General science and astronomy journals, 
such as Science and The Astronomical Journal, and even more so the specialized planetary sci- 
ence journals, such as Icarus and Earth, Moon, and Planets, remained forums for publica- 
tion. In addition, because they had added the planetary geology community to their audi- 
ence, radar astronomers now published in the Journal of Geophysical Research and 
Geophysical Research Letters. 

The new audience also shaped radar astronomy funding, although less so at the 
Arecibo Observatory, where the NSF-NASA agreement assured an annual budget for 
radar astronomy research. Researchers elsewhere seeking NASA money for planetary sur- 
face studies faced the demands of the NASA planetary geology program. When Dick 
Simpson or Len Tyler, for instance, applied for geology program funds to study planetary 
surfaces, geologists reviewed their proposals. One of the frequent comments by those 
reviewers was that the proposal should include a geologist on the science team. As a result, 
Dick Simpson approached USGS Menlo Park geologist Henry Moore to collaborate with 
him. 77 Through their role as proposal reviewers, then, planetary geologists began to shape 
radar astronomy research proposals. 

Throughout the 1970s, as planning for Magellan and the flight of Pioneer Venus 
took place, the field of radar astronomy, measured in terms of active practitioners and 
telescopes, grew smaller. In 1980, the Arecibo Observatory was essentially the sole active 
telescope; it supported four active investigators. In contrast to this Little Science reality 
stood the Big Science of Magellan. Around a single radar instrument, the big-budget, 
multi-year mission organized individual scientists into groups that crossed turf boundaries 
(radar astronomy versus Stanford "space exploration") and that fostered common inter- 
ests among fields (planetary radar and geology scientists) . 

Although the exploration of planetary surfaces with space-based radars seemed to 
invigorate radar astronomy, the space-based approach has its limits in an era of budgetary 
limits. Cassini probably will be the last mission to carry a radar experiment into space. As 
currently conceived, Cassini will explore Saturn's cloud-covered moon, Titan, with a SAR. 
No other solar system bodies have impenetrable atmospheres that lend themselves to 
radar investigation. The problem of transmitting data back to Earth at distances beyond 
the orbit of Saturn is a major, though not insurmountable obstacle (as Voyager has 
shown). The use of laser rather than radar altimeters on future missions means that mod- 
ifying the altimeter to carry out imaging, as was done on Pioneer Venus, has reached its 
technological limit (although military research may well yield a laser altimeter capable of 
imaging). 

However, the most formidable barrier to any future mission is the shrinking space 
and national budgets. The Voyager, Galileo, and Magellan spacecraft were expensive, cost- 
ing $2-3 billion, huge, standing seven meters high, as tall as most homes, and heavy, 
weighing several tons. Galileo, for example, weighed three tons. In order to accommodate 
a future of smaller budgets, NASA has initiated the Discovery program, in which low-cost 
($150 million limit) small, lightweight spacecraft with limited scientific objectives carry 



76. Campbell 9 December 1993. 

77. Simpson 10 May 1994. 



204 TO SEE THE UNSEEN 



out solar system exploration. One problem with this approach is that missions to Jupiter 
and Saturn or beyond simply cost too much to fit the budgetary limits set for Discovery 
missions. 78 Such is the price of practicing science on a large scale. 

Magellan also effectively ended ground-based radar observations of Venus. Although 
a few experiments were still possible, for example, the detection of rain on Venus with an 
X-band radar or polarization studies of surface scattering properties, 79 they likely will not 
achieve prominence. Indeed, Don Campbell, who has spent his scientific career doing 
radar studies of Venus, volunteered to Nick Renzetti of JPL at the Lunar and Planetary 
Conference at Houston in 1985 that he was not likely to do any more Venus observations; 
instead, he planned to concentrate on asteroid and comet experiments. 80 

Campbell typified the new direction that planetary radar astronomy began taking 
after 1975, when the Arecibo and Goldstone upgraded radars became available. 
Technology still drove planetary radar astronomy. New and better instruments and inno- 
vative techniques allowed radar astronomers to solve problems previously unsolvable and 
to detect and study solar system objects never before explorable with radar. The explo- 
ration of those objects in turn presented unusual radar characteristics that led radar 
astronomers to solve new scientific problems. The dynamic resonance between radar tech- 
niques (epistemological issues) and problem solving (scientific questions) thus remained 
at the heart of planetary radar astronomy. Nonetheless, despite a short spurt of growth 
following the inauguration of the upgraded Arecibo and Goldstone radars, by 1980 the 
planetary radar literature had reached a plateau of activity; the field had reached the 
limits to its growth. 



78. Richard A. Kerr, "Scaling Down Planetary Science," Science 264 ( 1994) : 1244-1246. 

79. Goldstein 14 September 1993; Pettengill 4 May 1994. Bill Smith tried to look for rain in Venus' 
atmosphere at the Haystack Observatory in the 1960s. Smith 29 September 1993. 

80. GSSR Min. 28 March 1985. 



Chapter Eight 

The Outer Limits 



Planetary radar astronomy was a problem-solving activity, an algorithm in search of 
a problem. Its fundamental driving force was the dynamic interaction between radar tech- 
niques and the kinds of problems radar astronomy solved. Improvements in radar hard- 
ware and innovative radar techniques, such as range-Doppler mapping, allowed radar 
astronomy to solve scientific problems of interest to astronomers and geologists. 
Conversely, problem-solving could bring attention to radar techniques and properties pre- 
viously neglected or little used, such as the polarization of echoes. 

The institutional and financial linking of radar astronomy to NASA at Arecibo and 
JPL gave the field a mission-oriented cast. The justification for funding was the field's 
utility to NASA space missions, and access to Goldstone antenna time required specific 
mission support. Beginning with Viking, participation in NASA missions also brought 
ground-based radar astronomers into closer collaboration with the radar scientists at the 
Stanford Center for Radar Astronomy. The distinction made in the 1960s between 
ground-based planetary radar astronomy and Stanford's "space exploration" held less and 
less meaning. 

Planetary radar astronomy after about 1975 also remained above all else a science 
driven by technology, namely, access to radars with the transmitter power and antenna 
and receiver sensitivity to explore the planets. Without those radars, radar astronomy 
could not exist. The decline of radar astronomy at JPL followed directly from the deteri- 
orating state of the Goldstone radar. Improvements in radar hardware, on the other hand, 
drove planetary radar forward. 

Additional transmitter power and receiver sensitivity meant access to previously 
unexplored targets. The orbit of Mars defined the outer reaches of planetary radar astron- 
omy until 1975, when both the Arecibo and Goldstone radars underwent upgrades that 
significantly enhanced their value as research tools, as discussed in Chapter Four. For the 
first time, the Galilean satellites of Jupiter, the rings of Saturn, cometary nuclei, and a 
number of both Earth-approaching and mainbelt asteroids came within reach of those 
planetary radars. Those targets represent considerable radar distances; the round-trip 
radar time to the moons of Jupiter is about 1 hour and 12 minutes and to Saturn's rings 
around 2 hours and 15 minutes. 

Meanwhile, the planetary radar astronomy community remained small, and Arecibo 
and Goldstone were the only active research facilities. Arecibo was still a major NSF-fund- 
ed center for radio astronomy and ionospheric research. On the other hand, funded by 
NASA, not the NSF, and associated with exploration of the solar system, radar astronomy 
there occupied a small, peculiar niche, a niche that, nonetheless, furnished a research 
facility for both Cornell and MIT graduate students to be trained as future radar 
astronomers. 

In contrast, Goldstone did not train graduate students. The radar astronomers at JPL 
did not hold the kind of appointment at Caltech that permitted them to train graduate 
students as future radar astronomers, and no Caltech professor was interested in training 
radar astronomers. A similar situation had existed at Lincoln Laboratory during the 1960s 
until Pettengill's appointments at Arecibo and his subsequent teaching position at MIT 
changed that situation and provided the institutional matrix for the training of graduate 



205 



206 TO SEE THE UNSEEN 



students as future radar astronomers. In short, the teacher-disciple pattern that prevailed 
at Arecibo was lacking at JPL, where radar astronomers propagated through job hiring. 
Planetary radar astronomy at JPL remained unofficial and invisible. Between 1978 and 
1986, furthermore, essentially no radar astronomy work took place at Goldstone, because 
investigators lacked a reliable research instrument. 

The Galilean Moons of Jupiter 

Among the new radar targets brought into range by the Goldstone X-band and 
Arecibo S-band upgrades were Ganymede, Eurcpa, Callisto, and lo, named the Galilean 
moons of Jupiter after their discoverer, Galileo Galilei. The radar exploration of those 
moons illustrated the interactions between radar astronomers and geologists, as well as 
the increasing collaboration with Stanford researchers that came to typify ground-based 
planetary radar. Those moons also puzzled radar astronomers. Never before had they 
encountered such peculiar radar characteristics among the terrestrial planets. An expla- 
nation for the bizarre radar readings came from Earth and from leading edge research in 
the physics of light. 

The first, though unsuccessful, attempt at the Galilean moons took place in 1970. 
Dick Goldstein (at Goldstone) and Dick Ingalls and Irwin Shapiro (at Haystack) tried to 
detect echoes from Callisto using the bistatic Goldstack radar, in which the Haystack 
300-kilowatt telescope transmitted and Goldstone received. 1 The experiment did not 
work, however, because of a misunderstanding over polarization. 

After unsuccessfully attempting Venus with the Goldstack radar, Ingalls and 
Goldstein pointed the radar at the Moon and received "the weakest of signals." Goldstein, 
trained as an electrical engineer, realized what was wrong. Bistatic radars require investi- 
gators to agree on the polarization of the wave. Physicists, like Shapiro, use one definition 
for left-handed polarization, defining handedness from the view of a person looking in 
the direction that the wave is travelling, while electrical engineers use the opposite con- 
vention, defining handedness from the view of the receiving antenna, so left and right are 
reversed. Goldstack eventually searched for Ganymede and Callisto in late May and early 
June 1970. 2 The polarization of radar echoes was about to become a key radar technique 
for studying the Galilean moons and other solar system bodies. 

Dick Goldstein and George A. Morris succeeded in detecting Ganymede with the 400 
kilowatts of Goldstone S-band radar power on six nights in late August 1974. Those echoes 
set a record for the longest time of flight to a radar target, one hour and seven minutes. 
The echoes, though, were very weak, well below the noise level. From those weak echoes, 
Goldstein and Morris drew conclusions about the surface of Ganymede. 

From the total signal power returned and the width of the spectrum, they conclud- 
ed that Ganymede "must have a considerable degree of roughness." Their data did not 
agree with accepted theory, derived from infrared spectra and polarization studies, that 
Ganymede's surface consisted mostly of ice. 3 Goldstein and Morris ventured that the most 



1. Referred to in Campbell, Chandler, Pettengill, and Shapiro, "Galilean Satellites of Jupiter: 12.6- 
Centimeter Radar Observations," Science 196 (1977): 650. 

2. Shapiro 1 October 1993; "Funding Proposal, 'Plan for NEROC Operation of the Haystack Research 
Facility as a National Radio/Radar Observatory,' NSF, 7/1/71-6/30/73," 26/2/AC 135, and Sebring to 
Hurlburt, 27 March 1970, 18/2/AC 135, MITA; NEROC, Proposal to the National Science Foundation for 
Programs in Radio and Radar Astronomy at the Haystack Observatory, 8 May 1970, pp. III.8- III. 10, LLLA; JPL 
1970 Annual Report, p. 14, JPLA. 

3. See Joseph Veverka, "Polarization Measurements of the Galilean Satellites of Jupiter," Icarus 14 
(1971): 355-359; John S. Lewis, "Low Temperature Condensation from the Solar Nebula," Icarus 16 (1972): 
241-252. Although lo, Ganymede, and Europa were believed covered with frost, Callisto was believed to be dif- 
ferent, more like the Moon, though with some frost possibly present. 



THE OUTER LIMITS 207 



likely possibility was for the surface to consist of rocky or metallic material from meteoric 
bombardment embedded in a matrix of ice. 4 

Soon after the Arecibo S-band upgrade reached completion, Don Campbell (NAIC 
Research Associate) and Gordon Pettengill (MIT) made the first radar detections of 
Callisto and Europa on 28 September and 5 October 1975, respectively, and detected 
Ganymede on 30 September. Pettengill and Campbell noticed that the satellites had an 
unusual radar signature. The three moons were almost uniformly radar bright; they 
lacked the bright specular return from the subradar point, the area on the target closest 
to the Earth, that all terrestrial planets exhibit. The uniformity of brightness suggested 
tiiat the satellite surfaces were probably extremely rough on scales comparable to or larg- 
er than the wavelength of 12 cm. 

lo remained an elusive radar target. The innermost of the Galilean moons, lo is 
inside Jupiter's magnetosphere, which may have interfered with the radar waves aimed at 
lo. Campbell and Pettengill unsuccessfully attempted the satellite twice in 1975, and their 
attempt to detect lo in January 1976 yielded only a weak echo that indicated an error in 
the ephemeris large enough to explain the previous failed attempt. Not until 1987, when 
improved hardware was available, did radar astronomers begin to receive good echoes 
from lo. 

After reducing their January 1976 data on the four Galilean moons, Campbell and 
Pettengill found surprisingly large radar cross sections for Europa and Ganymede, 
approximately 1 .5 and 0.9 times the geometric cross section, respectively, while those for 
Callisto and lo were around 0.4 and 0.2, respectively. The radar cross section is a measure 
of target brightness. Although the values for Callisto and lo were low and typical of the 
terrestrial planets, the radar cross sections for Europa and Ganymede were abnormally 
high. 5 

When Pettengill and Campbell resumed their observations of Jupiter's moons in 
October 1976, the Arecibo radar had a dual polarized circular feed paid for with NASA 
S-band operations funds. The feed increased total system sensitivity over that available in 
1975 and displayed the peculiar radar polarization properties of the Galilean satellites. 

Previously, all observations of the Galilean moons had been made with linear feeds 
in both orthogonal linear polarizations. The transmitter sent out signals with one sense of 
polarization, and the antenna received both the same linear and orthogonal linear polar- 
izations. The same linear echoes are much stronger than the orthogonal linear echoes for 
all targets detected by radar. Although the switch from linear to circular polarization did 
not alter the general character of the spectra for Callisto, Ganymede, and Europa, the cir- 
cular polarization ratios of the echoes were totally unanticipated. 

When radar astronomers transmit a right-handed circularly polarized signal, they 
expect the echo to return mostly left-handed circularly polarized, the opposite handed- 
ness. This type of polarization return is called variously the "expected," "polarized," or 
"opposite circular" (OC). The echo power returned right-handed circularly polarized is 
said to have "unexpected," "depolarized," or "same circular" (SC) polarization. The SC-to- 
OC ratio is known as the circular polarization ratio. 

The terminology "expected" and "unexpected" is out of place today. The "unex- 
pected" polarization returns from the Galilean moons and other icy targets are no longer 
considered unusual or "unexpected." The terms, however, reflected the surprise of radar 
astronomers in the past, as they discovered polarization returns that differed markedly 
from those of the terrestrial planets. For the sake of preserving that historical flavor of dis- 
covery, and to avoid using terms likely unfamiliar and perhaps confusing to the reader 
(such as "polarized" and "depolarized"), the terminology "expected" and "unexpected," 
or OC and SC, will be used throughout. 



4. Goldstein and Morris, "Ganymede: Observations by Radar," Science 188 (1975): 1211-1212. 

5. Campbell 8 December 1993; NAIC QR Q3/1975, 4-5; NAIC QR Q4/1975, 5; NAIC QR Ql/1976, 6. 



208 TO SEE THE UNSEEN 



In radar observations of the terrestrial planets and the Moon, more power normally 
returns in the expected than in the unexpected mode. The circular polarization ratio for 
these targets is about 0.1; for Venus and the Moon, it is only about 0.05. In the case of 
Jupiter's moons, however, more power returned in the unexpected mode, a phenomenon 
called circular polarization inversion. For Europa, Ganymede, and Callisto, the average 
circular polarization ratios were 1.61 0.20, 1.48 0.27, and 1.24 0.19, respectively. They 
were the first solar system objects for which circular polarization inversion was observed. 6 

The dominance of unexpected polarization from the Galilean satellites was enig- 
matic and even unbelievable. "That was a bit of a puzzle," Don Campbell recalled. 'There 
was a lot of skepticism, frankly, about the results.... That was a really significant puzzle to 
everybody." 7 The phenomenon was also a puzzle to Steve Ostro, then a graduate student 
at MIT working under Gordon Pettengill. Ostro was looking for a dissertation topic. He 
joined Pettengill and Campbell in observing the Galilean satellites at Arecibo in late 1976. 
'The anticipation," Ostro explained, "was that working on those observations, as well as 
on the data reduction and interpretation, would evolve into a good thesis topic." 8 

When the bizarre circular polarization inversion first appeared during the 26 
October through 7 December 1976 observations, Ostro recalled, "We tested to the point 
of grasping at straws. Maybe we had crossed the cables. Or maybe somebody had screwed 
up in the data acquisition program. We checked everything. We couldn't believe it, just 
couldn't believe it." A test on Venus returned normal echoes. Then they pointed the tele- 
scope at Europa, and the circular polarization ratio was about one and a half. At that 
point, Ostro remembers watching Pettengill reflecting then saying, "Well, now I have to 
believe it." Then he turned to Ostro and said, "If you can explain this, it would be a good 
thesis topic." 9 

In order to investigate systematically the unusual radar cross sections and polariza- 
tion ratios of the Galilean moons, Ostro, Campbell, and Pettengill undertook a new series 
of 20 observation sessions in November and early December 1977 and obtained results 
similar to those found the previous year. 10 

Ostro, Pettengill, and Campbell continued their campaign on the Galilean satellites 
in February 1979 and March-April 1980, when the satellites were in different phases. Also, 
in order to determine whether the strange polarization ratios were a function of fre- 
quency, Don Campbell undertook a separate series of observations with the old 430-MHz 
(70-cm) radar and obtained a weak detection of Europa, but not of Ganymede. 11 Jupiter 
then left the declination window of the Arecibo Observatory until 1987. 

In order to account for the unusual radar signatures of Europa, Ganymede, and 
Callisto, Steve Ostro developed a model, published in 1978. The model postulated a thick 
surface layer of ice saturated with nearly hemispherical surface craters. Hemispherical 
craters would favor double reflection of radar waves at a 45 angle at each reflection, so 
that most of the signal would return with the same handedness of polarization. The same 
craters could be made to explain the high radar cross sections, as well. 12 



6. Campbell, Chandler, Pettengill, and Shapiro, "Galilean Satellites of Jupiter: 12.6-Centimeter Radar 
Observations," Science 196 (1977): 650-653; Campbell, Chandler, Steven J. Ostro, Pettengill, and Shapiro, 
"Galilean Satellites: 1976 Radar Results," Icarus 34 (1978): 254-267; NAIC QR Ql/1976, 17; Ostro, "Radar 
Properties of Europa, Ganymede, and Callisto," in David Morrison, ed., Satellites of Jupiter (Tucson: University of 
Arizona Press, 1982), p. 213. 

7. Campbell 8 December 1993. 

8. Ostro 18 May 1994; NAIC QR Ql/1976, 6. 

9. Ostro 18 May 1994. 

10. Campbell, Chandler, Ostro, Pettengill, and Shapiro, "Galilean Satellites: 1976 Radar Results," Icarus 
34 (1978): 254-267; Ostro, "The Structure of Saturn's Rings and the Surfaces of the Galilean Satellites as Inferred 
from Radar Observations," Ph.D. dissertation, MIT, 1978; NAIC QRQ4/1977, 5-6; NAIC QR Ql/1978, 6. 

1 1 . Ostro, Campbell, Pettengill, and Shapiro, "Radar Observations of Europa, Ganymede, and Callisto," 
Icarus44 (1980): 431-440; NAIC QRQ1/1979, 10; NAIC QRQ2/1980, 11. 

12. Ostro and Pettengill, "Icy Craters on the Galilean Satellites?" Icarus 34 ( 1978): 268-279. 



THE OUTER LIMITS 209 



Dick Goldstein and Richard R. Green at JPL proposed a different model based on 
their own observations of the Galilean satellites. After the pioneering observations of 1974 
at S-band, Goldstein took additional data on Ganymede during six nights in December 
1977 with the Goldstone X-band radar and received alternately right-handed and left- 
handed circular polarization, in order to compare the expected and unexpected echo 
strengths. Despite the high transmitter power (343 kilowatts) and low system noise 
temperature (23 K), the Ganymede echoes were noisy. Nonetheless, the Goldstone data 
confirmed the Arecibo results, which had been the subject of great incredulity. As Don 
Campbell recalled, 'That confirmation started a significant discussion about the 
phenomenon. Why were we getting these odd reflections?" 13 

From the spectral data, Goldstein and Green measured the radar cross section and 
polarization ratios and posited a model of Ganymede's surface. They assumed that the 
upper few meters of its surface consisted of ice "crazed and fissured and covered by jagged 
ice boulders." The critical part of the model was a large number of interfaces between ice 
and vacuum where, depending on the angle of incidence above or below a certain limit 
(called the critical angle), the sense of polarization was largely preserved and most of the 
power remained in the original polarization sense. In a 1982 review article, Steve Ostro 
concluded that "many questions remain about interpretation of the radar results, but we 
seem to be pointed in a sensible direction." 14 

Voyager 1 had begun sending back pictures of the Jupiter system in early 1979. 
Geologic activity on Ganymede appeared varied, while Callisto's entire surface was 
densely cratered. Europa probably was covered completely by ice. 15 More information 
than ever was available about the surfaces of the Galilean satellites, yet none of it resolved 
the questions raised by planetary radar astronomers, who, in the meantime, attempted to 
explain the strange radar characteristics of the Galilean satellites based on reflection 
geometries and radar scattering rules, not the geology of those worlds as revealed by 
Voyager imagery. 

Among those offering explanations for the high cross section and circular polariza- 
tion inversion was Tor Hagfors. He proposed that the satellites' unusual radar signatures 
were due not to reflections at the interfaces of ice and vacuum, as Goldstein and Green 
had suggested, but rather to the bending of the incident wave around continuous gradi- 
ents in refractive index. 16 Von Eshleman developed an argument around refraction 
scattering from imperfect spheroidal lenses. Then he modified his argument and 
incorporated Ostro's notion of hemispheroidal impact craters, as well as elements from 
the Goldstein-Green model. 17 

The Ostro, Goldstein-Green, Hagfors, and Eshleman models all rested on radar 
geometries and scattering mechanisms. Not a single model linked surface or subsurface 
structure realistically to the radar signatures, nor did the models explain the origins of 
those structures. Positing the existence of hemispherical craters was one thing; finding 
geologic evidence for them was another. Not surprisingly, Voyager revealed no hemi- 
spherical craters on any of the Galilean satellites. Ostro now sought an explanation for the 
radar signatures of the Galilean moons in collaboration with USGS planetary geologist 
Eugene Shoemaker. 



13. Campbell 8 December 1993. 

14. Goldstein and R. Green, "Ganymede: Radar Surface Characteristics, " Science 207 (1980): 179-180; 
Ostro, "Radar Properties of Europa, Ganymede, and Callisto," in Morrison, Satellites of Jupiter, pp. 225-233, and 
quote p. 235. 

15. Morrison and Jane Samz, Voyage to Jupiter, NASA SP-439 (Washington: NASA, 1980), pp. 58, 60 
and 142. 

16. Hagfors, Gold, and M. lerkic, "Refraction Scattering as Origins of the Anomalous Radar Returns of 
Jupiter's Satellites," Nature 315 (1985): 637- 640. 

17. Eshleman, "Mode Decoupling during Retrorefraction as an Explanation for Bizarre Radar Echoes 
from Icy Moons," Nature 319 (1986): 755-757; Eshleman, "Radar Glory from Buried Craters on Icy Moons," 
Science 234 (1986): 587-590. 



210 TO SEE THE UNSEEN 



Shoemaker had a rather simple and elegant geologic solution to the problem. In 
developing his solution, Shoemaker drew upon his knowledge of the lunar regolith and 
Voyager data. He assumed that the surfaces of the Galilean moons were exactly like that 
of the Moon. From statistics of craters observed in Voyager images of Ganymede and 
Callisto, Shoemaker inferred that the surfaces of those moons had a history of meteor 
bombardment similar to that of the Moon. He concluded that they were probably 
blanketed with fragmental debris produced by prolonged meteoroid bombardment. The 
only difference, then, between the Moon and Jupiter's moons was that the rocks on the 
Galilean satellites were made of ice, and the ice, given the extremely low ambient 
temperatures, would behave like a silicate rock. Ice is highly transparent to radar waves, 
so the icy surfaces of the Galilean moons would permit radar waves to penetrate those sur- 
faces to a far greater extent than if they were made of silicate rock. The combination of 
the greater penetrating depth and the greater number of scattering events could provide 
an explanation for the peculiar radar signatures of the Galilean satellites. 18 

The primary contribution of the Ostro-Shoemaker model was its geological per- 
spective. Nonetheless, the model only partially explained the radar results; a satisfactory 
understanding of the detailed scattering mechanism that gave rise to the odd radar sig- 
natures still remained beyond reach. Meanwhile, Steve Ostro and Don Campbell had 
begun a new series of radar observations of the Galilean satellites at Arecibo in 1987. 
Unlike the previous campaign, Stanford researchers under the leadership of Von 
Eshleman participated. Dick Simpson took data at Arecibo, while a graduate student, Eric 
Gurrola, was charged with the analysis. Tor Hagfors, who also was interested in experi- 
menting on the Galilean satellites for reasons similar to those of the Stanford researchers, 
joined their group. 

This new series of S-band observations was to provide thorough phase coverage for 
all three icy satellites (Ganymede, Callisto, and Europa). Started in November 1987, the 
campaign continued into 1988, then November-December 1989, January 1990, and 
February-March 1991, when Ostro observed the satellites at rotational and orbital phases 
chosen to fill in gaps in the 1987-1990 phase coverage. 19 Then Jupiter left the Arecibo 
declination window. 

At the same time, Arecibo obtained the first good echoes from lo. Its radar proper- 
ties were unlike those of the other Galilean satellites. Data collected in 1976 already had 
shown that lo's surface was significantly rougher on average than the terrestrial planets, 
but much smoother than the other Galilean moons. Its radar cross section and polariza- 
tion ratio were more typical of the inner planets, however, and argued strongly against the 
presence of significant quantities of surface ice. 20 

In parallel with the 2,380-MHz (12.6-cm) observations, Don Campbell studied the 
Galilean moons with the 430-MHz (70-cm) radar beginning in November 1988, the first 
time in 25 years that the UHF radar had been used in the continuous-wave mode. He 
detected Ganymede and Callisto, then in November-December 1989, made the first UHF 
detection of Europa. The purpose of the experiment was to compare the polarization 
properties of the Galilean satellites at both S-band and UHF. Campbell discovered that the 
echoes from Ganymede at UHF were reminiscent of those at S-band. Additional UHF 
measurements made in January 1990 apparently confirmed that the peculiar polarization 
ratios of the Galilean moons were independent of frequency. 21 



18. Shoemaker 30 June 1994; Ostro and Eugene M. Shoemaker, The Extraordinary Radar Echoes from 
Europa, Ganymede, and Callisto: A Geological Perspective," Icarus 85 (1990): 335-345. 

19. E-mail, Simpson to author, 9 November 1994; NAIC QR Q2/1987, 7; Q3/1987, 8-9; Q4/1987, 9; 
Q2/1988, 9; Q4/1988, 8; Q4/1989, 7; Ql/1990, 7; Ql/1991, 7; Ql/1992, 8. 

20. Campbell, Chandler, Ostro, Pettengill, and Shapiro, "Galilean Satellites: 1976 Radar Results," Icarus 
34 (1978): 254-267; NAIC QR Ql/1976, 6; Q4/1977, 5-6; Q2/1987, 7; Q3/1987, 8-9; Q4/1987, 9. 

21. NAIC QR Q4/1989, 7; Ql/1990, 7. 



THE OUTER LIMITS 2 1 1 



Steve Ostro, who now had a position at JPL, also observed the Galilean satellites with 
the Goldstone X-band radar between 1987 and 1991 and measured polarization ratios and 
radar cross sections. The combined X-band, S-band, and UHF radar data taken over a 
long period of time documented the degree to which the satellites' radar properties 
depended on target, rotational phase, and frequency. 22 They provided a considerable base 
upon which to explain the bizarre radar signatures of the Galilean moons, and a reason- 
able explanation soon was in hand. 

Toward the end of the Arecibo and Goldstone campaign on the Galilean satellites, 
Bruce Hapke, an optical astronomer and scattering expert, drew attention to a growing 
body of literature on laboratory and theoretical investigations of a phenomenon called 
alternatively "coherent-backscatter effect" or "weak localization." The effect has potential 
application in a new class of semiconductors in which photons, rather than electrons, per- 
form circuitry functions. Weak localization of light takes place at the microscopic level 
and arises from a combination of coherent multiple scattering and interference. 
Backscattered intensity is enhanced, and the forward diffusion through the low-loss medi- 
um reduced, by constructive interference between fields propagating along identical but 
time-reversed paths. 23 

At the suggestion of Steve Ostro, Kenneth J. Peters of Caltech did calculations that 
demonstrated that coherent backscattering from forward scatterers could explain the 
high reflectivity and polarization ratios of the Galilean satellites. 24 Coherent backscatter- 
ing now appeared to explain adequately the high radar cross sections and circular polar- 
ization ratios of the icy satellites, and it was consistent with the geologic picture of those 
moons painted by Gene Shoemaker. The scattering might arise less from individual pieces 
of ejecta, but more likely from uncoordinated changes in porosity (and hence refractive 
index) that occur randomly throughout "smoothly heterogeneous" regoliths, argued 
Ostro and Shoemaker. 25 

Additional data on the radar properties of icy surfaces came from observations of the 
Earth. In June 1991, the NASA/JPL airborne synthetic aperture radar (AIR-SAR) flew 
over a vast portion of the Greenland ice sheet called the percolation zone, where summer 
melting generates water that percolates down through the cold, porous dry snow then 
refreezes in place to form massive layers and pipes of solid ice. The AIR-SAR radar 
observed the Greenland ice sheet at several wavelengths (5.6-, 24-, and 68-cm) and 
obtained values for the circular polarization ratio greater than one. 26 

The riddle of the strange radar signatures of the Galilean satellites focused radar 
astronomers' attention on epistemological questions, the fundamental need to under- 
stand and interpret radar echoes and their relationship to the target. Such questions, 
though, were of interest only to radar astronomers; their solutions contributed to an 



22. Ostro, Campbell, Simpson, R. Scott Hudson, Chandler, Keith D. Rosema, Shapiro, Standish, R. 
Winkler, Donald K. Yeoman, Ray Velez, and Goldstein, "Europa, Ganymede, and Callisto: New Radar Results 
from Arecibo and Goldstone ," Journal of Geophysical Research 97 (1992): 18,227-18,244. The Goldstone observa- 
tions were made 10-11, 13, 15-16, 22, 26, and 29-30 November 1988; 5 and 8 December 1988; 13, 14, 15, 18, 
19, 20, 22, 24, 27, and 29 December 1989; 13, 18, 22 and 27 December 1990. 

23. Ostro 18 May 1994; Bruce Hapke, "Coherent Backscatter and the Radar Characteristics of Outer 
Planet Satellites," Icarus 88 (1990): 407-417; Hapke and David Blewett, "Coherent Backscatter Model for the 
Unusual Radar Reflectivity of Icy Satellites," Mz/r352 (1991) 46-47; Sajeevjohn, "Localization of Light," Physics 
Today 44 (May 1991): 32-40. 

24. Kenneth J. Peters, "Coherent-Backscatter Effect: A Vector Formulation Accounting for Polarization 
and Absorption Effects and Small or Large Scatterers," Physical Review B 46 (1992): 801-812; John, "Localization 
of Light," Physics Today 44 (May 1991): 32-40; Ostro 18 May 1994. 

25. Ostro 18 May 1994; Ostro and Shoemaker, The Extraordinary Radar Echoes from Europa, 
Ganymede, and Callisto: A Geological Perspective," 7ean85 (1990): 335-345. 

26. Eric J. Rignot, Ostro, Jakob J. Van Zyl, and K, C. Jezek, "Unusual Radar Echoes from the Greenland 
Ice Sheet," Scin261 (24 September 1993): 1710-1711. 



212 TO SEE THE UNSEEN 



understanding of the radar characteristics of planetary surfaces, but not to the more gen- 
eral scientific questions posed by non-radar planetary astronomers. However, if radar 
astronomers were going to contribute to our knowledge of the Jupiter and Saturn systems, 
they first had to resolve such basic epistemological issues relating to the radar properties 
of those planetary systems. 

Although the central focus of radar research on the Galilean satellites had been the 
solution of the satellites' strange radar signatures, the data also has served to correct their 
ephemerides as part of the Planetary Ephemeris Program of Irwin Shapiro and John 
Chandler of the Harvard-Smithsonian Center for Astrophysics. The radar data uncovered 
errors in the ephemerides as early as 1976. A round of Callisto observations carried out 
beginning in 1987, though, were intended mainly for orbital ephemeris refinement in 
support of the Galileo mission. 27 

Sensitized to the needs of planetary geologists, Ostro also attempted to relate radar 
data collected at Arecibo and Goldstone between 1987 and 1991 to surface features on the 
Galilean moons. The most prominent features tentatively identified in the echo spectra 
were Ganymede's Galileo Regio and Callisto's Valhalla Basin. 28 Using a new radar coding 
technique, John Harmon and Steve Ostro observed Ganymede and Callisto at Arecibo 
from February to March 1992 and obtained the first range-Doppler images of the moons. 
These observations also constituted the first successful ranging measurements to the 
Galilean satellites and the farthest radar distance measurements ever reported. 29 

The exploration of the Galilean moons of Jupiter illustrated the increasing com- 
plexity of the planetary radar paradigm. Hardware improvements, coding techniques, and 
even discoveries made in optics laboratories shaped the science done by radar 
astronomers. Moreover, despite the shift toward geology, planetary radar remained ori- 
ented toward astronomical questions and NASA missions, such as Galileo. 

The Outer Limits 

The rings of Saturn, like the Galilean moons of Jupiter, presented radar astronomers 
with a target very different from the terrestrial planets. The rings of Saturn were believed 
to be icy and until the 1970s, were thought to consist of tiny, micron-sized particles. Radar 
astronomy upset that conception of the rings. In doing so, radar astronomy also set a dis- 
tance record: the round-trip light time to the rings was about 2 hours and 15 minutes. 

After an unsuccessful try in 1967, Haystack researchers successfully bounced X-band 
radar waves off the rings in 1973. 30 Earlier, however, in December 1972 and January 1973, 
Richard Goldstein and George A. Morris, Jr., at JPL detected the rings with the S-band 
Goldstone Mars Station. Making the observation was not easy. The orientation of the rings 
is optimum for radar observations only twice during each 29-year orbit of Saturn, when 
the rings are most tilted to the line of sight and present the largest projected area. At the 
same time, the Doppler spreading and consequent dilution of the signals in the noise is 
the least. 



27. NAIC QR Ql/1976, 7; Q4/1977, 5-6; Q3/1987, 8-9; Q2/1988, 9; Ql/1992, 8; Campbell, Chandler, 
Pettengill, and Shapiro, "Galilean Satellites of Jupiter: 12.6-Centimeter Radar Observations," Science 196 (1977): 
651; Ostro, Campbell, Simpson, Hudson, Chandler, Rosema, Shapiro, Standish, Winkler, Yeoman, Velez, and 
Goldstein, "Europa, Ganymede, and Callisto: New Radar Results from Arecibo and Goldstone," Journal of 
Geophysical Research 97 (1992): 18,227-18,244. 

28. Ostro, Campbell, Simpson, Hudson, Chandler, Rosema, Shapiro, Standish, Winkler, Yeoman, Velez, 
and Goldstein, "Europa, Ganymede, and Callisto: New Radar Results from Arecibo and Goldstone, "Journal of 
Gerfhysical Research 97 (1992): 18,227-18,244; NAIC QRQ1/1991, 7. 

29. Ostro, Pettengill, Campbell, Goldstein, Icarus 49 ( 1982) : 367. 

30. NEROC, Final Progress Report Radar Studies of the. Planets, 29 August 1974, pp. 1,3,6 and 8-9; Log Book, 
Haystack Planetary Radar, HR-73-1, 27 June 1973 to 26 November 1973, SEBRING; and Goldstein, R. Green, 
Pettengill, and Campbell, "The Rings of Saturn: Two-Frequency Radar Observations," Icarus 30 (1977): 105. 



THE OUTER LIMITS 2 1 3 



The echoes Goldstein and Morris found were unexpectedly strong. The rings were 
inclined at an angle about 26 with respect to the line of sight, and the amount of power 
returned from the rings was about 10 times that for Mercury and five times that for Venus. 
Moreover, wrote Goldstein and Morris: "Particles of any material that are much smaller 
than our wavelength [12.6 cm] are ruled out by our data.. ..Large (compared to the wave- 
length), irregular, rough particles could produce the observed echoes." 31 

Shortly thereafter, on 31 July and 1 August 1973, JPL organized a workshop on 
Saturn's rings at the request of S. Ichtiaque Rasool of the Planetary Programs Office, 
NASA Headquarters. Gordon Pettengill organized the scientific program. The workshop 
responded to an upsurge in interest in the Saturn system, and the outer systems in gen- 
eral, in anticipation of the 1977 Mariner Jupiter/ Saturn mission, later known as Voyager. 

The interpretation of the JPL radar experiment on Saturn's rings surprised 
astronomers 32 and caused rethinking about the ring particles and models published by 
radio astronomers. The amazingly large particle size also raised questions about the safe- 
ty of a spacecraft near the rings and gave rise to NASA and JPL interest in the radar results, 
which George Morris discussed at the workshop. Excited by the Goldstone radar findings, 
astronomers during the general discussion expressed an interest in obtaining more radar 
data on the rings. 33 

The JPL results also surprised radar astronomers. For example, Gordon Pettengill 
(MIT ) and Tor Hagfors (then at the Department of Electrical Engineering of the Norges 
Tekniske Hogskole, Trondheim, Norway) , based on their own radar experience with the 
terrestrial planets and the asteroids Icarus and Toro, felt that the radar cross section 
observed by Goldstein and Morris, 0.62 0.15, was unreasonably high. "Even by assuming 
the particulate matter in the rings to have linear dimensions comparable to or larger than 
the radar wavelength," they wrote, "we are left with the need to explain a radar scattering 
mechanism more efficient by a factor of about 10 than that of the inner planets, unless we 
wish to postulate an unreasonable ring particle density or composition." 34 

Astonished, too, were radio astronomers. The high radar return had to be reconciled 
with the rings's low radio emission, as well as with optical and infrared results. 35 As the 
enigma of Saturn's rings continued to puzzle astronomers, the Arecibo S-band upgrade 
reached completion. It seemed only natural, as Don Campbell explained, that the first 
radar experiment with the upgraded telescope should be an attempt to detect echoes 
from the rings of Saturn: "When Arecibo first came on line in 1974, the very first thing we 
did to test the transmitting system, apart from trying to communicate with a star system 
25,000 light years away, was to run a bistatic radar measurement on the rings of Saturn 



31. Goldstein and Morris, "Radar Observations of the Rings of Saturn," Icarus 20 (1973): 260-262; 
Morris, "Distribution and Size of Elements of Saturn's Rings as Inferred from 12-cm Radar Observations," in 
Frank Don Palluconi and Pettengill, eds., The Rings of Saturn, SP-343 (Washington: NASA, 1974), p. 73. 

32. Campbell 8 December 1993. See, for example, Allan F. Cook, Fred A. Franklin, and F. D. Palluconi, 
"Saturn's Rings: A Survey," Icarus 19 (1973): 317-337 and Pollack, "The Rings of Saturn," American Scientist 66 
(1978): 30-37. 

33. Rasool, "Foreword," in Palluconi and Pettengill, pp. v-vi; ibid., pp. 192-195; and Morris, 
"Distribution and Size of Elements of Saturn's Rings as Inferred from 12-cm Radar Observations," pp. 73-82. 
Interestingly, when a subsequent workshop on Saturn's rings was held at the Reston International Conference 
Center, Reston, Virginia, 9-11 February 1978, and sponsored by the NASA Office of Space Science, no radar pre- 
sentations were made. The purpose of the workshop was more tightly defined than the 1973 workshop; the 1978 
workshop strictly prepared for the Voyager mission. 

34. Pettengill and Hagfors, "Comment on Radar Scattering from Saturn's Rings," Icarus 21 (1974): 
188-190, esp. 188. 

35. Jeffrey N. Cuzzi and David Van Blerkom, "Microwave Brightness of Saturn's Rings," Icarus 22 (1974): 
149-158; Pollack, A. L. Summers, and B. Baldwin, "Estimates of the Size of the Particles in the Rings of Saturn 
and their Cosmogonic Implications," Icarus 20 (1973): 263-279; Morrison and D. P. Cruikshank, "Physical 
Properties of the Natural Satellites," Space Science Review 15 (1974): 722-732; Pollack, The Rings of Saturn," Space 
Science Review 18 (1975): 3-97. 



214 fTO SEE THE UNSEEN 



with Goldstone. At that time, we had transmitting capability, but we had not yet installed 
the receivers. The dedication of the upgraded telescope had been in November 1974, and 
this was in December, when we were trying to get the transmitter really working properly." 36 

Despite equipment difficulties at Arecibo, Goldstone received echoes from Arecibo 
by way of Saturn. 37 In addition to the bistatic Arecibo-Goldstone radar test on Saturn's 
rings in December 1974, Arecibo and Goldstone performed dual-polarization experi- 
ments on two nights in January 1975. These bistatic linear polarization experiments estab- 
lished that echoes from the rings of Saturn were highly depolarized, that is, more power 
appeared in the unexpected than in the expected polarization. 

Goldstein also conducted monostatic dual-polarization observations with the 
Goldstone X-band radar on five nights in December 1974 and January 1975 and measured 
a high circular polarization ratio. Goldstone and Arecibo investigators now knew that 
Saturn's rings exhibited high linear and circular polarization ratios and that the 
phenomenon was independent of frequency. Moreover, they confirmed at both X-band 
and S-band that the rings had high radar cross sections. 38 

The high radar cross sections and polarization ratios of Saturn's rings were puzzling. 
Campbell and Goldstein considered several possible explanations for those radar proper- 
ties. Two models appeared plausible. One model hypothesized a thick cloud of irregular 
water-ice chunks a few centimeters or larger in radius. The other posited a monolayer of 
multimeter-sized water-frost-coated metallic chunks. Voyager data later rejected the metal- 
lic composition of the rings. 39 In summing up the state of knowledge on Saturn's rings in 
1975, Allan F. Cook and Fred A. Franklin of the Smithsonian Astrophysical Observatory 
speculated that the ring particles consisted of water ice, clathrated hydrates of methane, 
and ammonia hydrates, 40 in agreement with one of the radar models. 

Meanwhile, James Pollack and other astronomers proposed that the ring system was 
diffuse and many particles thick. In order to determine whether the rings of Saturn con- 
sisted of one or several layers, and in general to test various models of the thickness and 
composition of the rings, Gordop Pettengill, Don Campbell, and Steve Ostro undertook 
further radar observations in 1977, 1978, and 1979 on a total of 13 nights. Like those on 
the Galilean satellites of Jupiter, the observations became part of Ostro's thesis. 41 In 
March 1977, also, Gordon Pettengill and Dick Goldstein resumed bistatic observations of 
Saturn's rings with the Arecibo and Goldstone S-band radars. 42 

The key to the radar observations made in 1977, 1978, and 1979 was the differing tilt 
angles of the rings during the 1 3 total nights of observations. The tilt angle of the rings 
relative to the line of sight declined over those three years from 18.2 to 11.7, then to 
5.6. The astronomers also received in both senses of circular polarization in order to 
measure the polarization ratio as a function of tilt angle. Their results, when combined 



36. Campbell 7 December 1993. 

37. NAICQRQ1/1975, 4. 

38. Goldstein, R. Green, Pettengill, and Campbell, "The Rings of Saturn: Two-Frequency Radar 
Observations, "Icarus 30 (1977): 104-110. 

39. L. W. Esposito, Cuzzi, J. B. Holberg, E. A. Marouf, Tyler, and C. C. Porco, "Saturn's Rings: Structure, 
Dynamics, and Particle Properties," in Tom Gehrels and Mildred Shapley Matthews, eds., Saturn (Tucson: 
University of Arizona Press, 1984), p. 46(j. 

40. Allan F. Cook and Fred A. Franklin, "Saturn's Rings: A New Survey," in Joseph A. Burns, ed., 
Planetary Satellites (Tucson: University of Arizona Press, 1977), pp. 412-419. See also Cuzzi and Pollack, "Saturn's 
Rings: Particle Composition and Size Distribution as Constrained by Microwave Observations." Icarus 33 (1978): 
233-262. , 

41. Campbell 8 December 1993; Esposito, Cuzzi, Holberg, Marouf, Tyler, and Porco, "Saturn's Rings: 
Structure, Dynamics, and Particle Properties," in Gehrels and Matthews, Saturn, p. 467; NAIC QR Ql/1978, 7; 
NAIC QR Ql/1979, 9; Ostro, "The Structure of Saturn's Rings," pp. 105-157. 

42. NAIC QRQ1 /1977,7. 



THE OUTER LIMITS 215 



with earlier radar data and the theoretical calculations of Jeffrey N. Cuzzi and James 
Pollack, 43 provided significant constraints on ring structure. 

The observations confirmed that the radar reflectivity of the rings was quite high and 
that depolarization was also high. The polarization ratio for the Galilean satellites, a 
mystery not yet solved, however, was higher. The data ruled out all large-particle mono- 
layer models. On the other hand, the polarization and radar cross section results favored 
ring models of several layers. The radar data also appeared to support particle composi- 
tion of ice or metal, but not silicate rock. 44 

Ostro, Pettengill, and Campbell also concluded that the A and B rings (the outer- 
most rings) were responsible for most, if not all, of the S-band radar echoes, and that the 
radar reflectivity of the A ring was nearly as great as the B-ring radar reflectivity. The radar 
reflectivity of the C ring was notably less than that of the B ring. Also, they found no evi- 
dence for radar echoes from beyond the A ring or from the planet itself. 45 

The case of Saturn's rings resulted in radar astronomers contributing to planetary 
science, in contrast to their studies of the Galilean moons. Those studies for a long time 
had been limited to epistemological issues, namely, what caused the Galilean moons' 
strange radar signatures? Radar contributed to Saturn science, on the other hand, by 
focusing less on such questions of radar technique and more on scientific questions, such 
as the size of the ring particles and the number and thickness of the ring layers. Although 
the solution of technical problems was a prerequisite for any radar astronomy problem 
solving, the lack of obvious relevance to planetary science was a serious matter; the abili- 
ty to solve scientific problems, especially those relating to NASA space missions, was the 
basis on which scientists judged the value of radar astronomy and on which funding deci- 
sions were made. 



Cometary Nuclei 



The nuclei of comets provided radar astronomers additional icy research subjects. 
Comets are believed to represent samples of the most primitive material of the solar neb- 
ula and to hold clues to the origin of the solar system. 46 They make challenging radar 
targets, because close approaches are rare. The relatively small size of comets dictates that 
they be studied by radar only when they approach Earth at distances of a fraction of an 
astronomical unit. Also, ephemerides derived from optical data lack the accuracy 
demanded for radar observations. Only the S-band and X-band upgrades of the Arecibo 
and Goldstone antennas made radar studies of comets possible. 



43. Cuzzi and Pollack, "Saturn's Rings: Particle Composition and Size Distribution as Constrained by 
Microwave Observations." Icarus 33 (1978): 233-262. 

44. Ostro, Pettengill, and Campbell, "Radar Observations of Saturn's Rings at Intermediate Tilt 
Angles," Icarus 41 (1980): 381-388. 

45. Ostro, Pettengill, Campbell, and Goldstein, "Delay-Doppler Radar Observations of Saturn's Rings," 
Icarus 49 ( 1982) : 367-381 . See also Ostro and Pettengill, "A Review of Radar Observations of Saturn's Rings," in 
A. Brahic, ed., Planetary Rings 1982 (Toulouse: CEPADUES Editions, 1982), pp. 49-55. 

Later radar data collected at Goldstone by Goldstein and Jurgens and at Arecibo by Ostro, Pettengill, and 
Campbell in 1981, when the rings were at a 6 tilt angle, confirmed that the ring particles were large, irregular, 
and jagged in shape and made of ice; the researchers finally abandoned the notion that they might be metallic. 
Moreover, they affirmed the conclusion that the A and B rings reflected most, if not all, of the radar echo from 
Saturn's rings. Goldstein and Jurgens, "Radar Observations of the Rings of Saturn, " Journal of Geophysical Research 
submitted for publication; Ostro, Pettengill, Campbell, and Goldstein, "Delay-Doppler Radar Observations of 
Saturn's Rings," Icarus 49 (1982): 367-381; Ostro, Pettengill, and Campbell, "Radar Observations of Saturn's 
Rings at Intermediate Tilt Angles," Icarus 41 (1980): 381-388. This research is summarized in: Ostro and 
Pettengill, "A Review of Radar Observations of Saturn's Rings," pp. 49-55. 

46. Whipple, "Comets," in J. A. M. McDonnell, ed., Cosmic Dust (New York: John Wiley & Sons, 1978), 
pp. 1-73. 



216 TO SEE THE UNSEEN 



Early attempts all ended in failure. For example, after an attempt in January 1971 on 
Comet Kohoutek stymied by rain and snow, the Haystack telescope again failed to detect 
that comet in January 1974. Although Irwin Shapiro had prepared an accurate ephemeris 
in advance, neither the bandwidth nor the center frequency of the radar echo was known 
precisely, so they had to search for the echo. 47 

It took the S-band upgrade of the Arecibo Observatory to make the first comet detec- 
tions possible. Paul G. D. Kamoun, a French student of Gordon Pettengill at MIT, built his 
dissertation research around those detections. The main objective of his dissertation was 
to use cometary radar data to discriminate between two different models of cometary 
nuclei. 48 One model was that proposed by Fred Whipple, who served on Kamoun's dis- 
sertation committee, and supported by Zdenek Sekanina, an established expert on 
comets. 

In the Whipple model, the cometary nucleus was like a rotating "dirty snowball," an 
icy matrix of water ammonia, methane, carbon dioxide, or carbon monoxide, combined 
with rock, dust and other meteoric debris. A popular model for the nucleus in the early 
20th century predicated a "dust swarm" or swarm of solid particles of unknown sizes, each 
particle carrying with it an envelope of gas, mostly hydrocarbons. However, that model 
had a number of difficulties, and by the 1970s Whipple's "dirty snowball" model pre- 
vailed. 49 Consequently, Kamoun's dissertation did not contribute meaningfully to the 
comet debate. 

Kamoun's research on comets turned around the unsuccessful cometary research 
begun at Arecibo by Gordon Pettengill, Brian Marsden (Harvard-Smithsonian 
Astrophysical Observatory) , and Irwin Shapiro (who prepared the ephemerides) . In late 
July 1976, they attempted to detect echoes from Comets d'Arrest and Grigg-Skjellerup 
during three observing sessions. Both attempts failed, although Comet d'Arrest came 
within 0.15 astronomical units of Earth. 50 

The first comet detected by radar was Comet Encke. As Don Campbell explained, "It 
was a historic first. We had never actually seen a comet before." 51 French and German 
astronomers had observed Encke earlier; its name came from the German mathematician 
and physicist Johann Encke, who initially suggested an elliptical orbit with a period of 12.2 
years, then correctly recalculated an elliptical orbit of 3.3 years, the shortest period of any 
known comet. 52 Comet Encke was due back in November-December 1980. Although 
Encke had a relatively stable and therefore predictable orbit, optical observations were 
neither sufficiently numerous nor sufficiently accurate to formulate a satisfactory 
ephemeris for the radar. Irwin Shapiro and Antonia Forni (Lincoln Laboratory) based 
the radar ephemerides on optical data from both past appearances and new observations 
associated with the 1980 appearance supplied by Brian Marsden. The ephemeris difficul- 
ties resolved, Kamoun, Campbell, and Ostro observed Encke for 12 hours on seven con- 
secutive days, 2-8 November 1980, about 30 days before the comet reached perihelion 
and at a distance of slightly more than 0.3 astronomical units from Earth. They found dis- 
tinct, but very weak, echoes during each observing session. 53 



47. Log book, Haystack Planetary Radar, HR-73-2, 9 December 1970 to 11 August 1971, SEBRING; 
Shapiro 1 December 1993; Eric J. Chaisson, Ingalls, Rogers, and Shapiro, "Upper Limit on the Radar Cross 
Section of the Comet Kohoutek," Icarus 24 (1975): 188-189. 

48. Paul Gaston David Kamoun, "Radar Observations of Cometary Nuclei," Ph.D. diss., MIT, May 1983. 

49. Whipple, "A Comet Model. I. The Acceleration of Comet Encke," Astrophysical Journal 111 (1950): 
375-394; Whipple, "A Comet Model. II. Physical Relations for Comets and Meteors," ibid., 113 (1951): 464-474. 

50. Kamoun, p. 31; NAIC QR Q3/1976, 6-7. 

51. Campbell 9 December 1993. 

52. John E. Bortle, "Comet Digest," Sky and Telescope 60 (1980): 290; Kamoun, pp. 37-38. 

53. Kamoun, p. 51; Kamoun, Campbell, Ostro, Pettengill, and Shapiro, "Comet Encke: Radar Detection 
of Nucleus," Science 216 (1982): 293-295; NAIC QR Q4/1980, 8-9. 



THE OUTER LIMITS 2 1 7 



Next, Kamoun attempted radar observations of the Comet Grigg-Skjellerup, which 
was discovered in 1902 by Grigg in New Zealand, then re-discovered as a new comet in 
1922 by Skjellerup in South Africa. Grigg-Skjellerup has an orbital period of 5.1 years, 
making it the second shortest periodic comet after Encke. The time of perihelion passage 
was 15 May 1982, at a perihelion distance of nearly one astronomical unit (0.989). 

Compared to other cometary experiments, Kamoun spent an unprecedented and 
never repeated 49 hours observing the comet between 20 May and 2 June 1982, about a 
week after it passed perihelion, while the comet was about 0.33 astronomical units from 
Earth. He received echoes in both senses of circular polarization, but technical problems 
prevented the acquisition of data on five days. An interesting feature was the very narrow 
(less than one Hz) Doppler bandwidth of the echo, which indicated either a very specu- 
lar echo, a slow rotation rate, or collinearity of the polar axis with the line-of-sight. 54 

Comet Austin came next. Unlike Encke and Grigg-Skjellerup, Comet Austin had 
only been discovered on the morning of 19 June 1982 by Rodney Austin in New Zealand. 
Alan Gilmore, of Mount John University Observatory, New Zealand, confirmed the dis- 
covery. The comet was first reported on 21 June 1982 in IAU circular 3705 of the Central 
Bureau for Astronomical Telegrams by Brian Marsden, who also computed and made pub- 
lic a set of orbital elements showing that the comet was moving on a parabolic orbit. From 
the Marsden ephemeris, it appeared that Comet Austin would pass close enough to Earth 
to detect it with the Arecibo radar. 

Following receipt of IAU circular 3706 containing the improved elements of the 
comet's orbit, Kamoun undertook the task of obtaining telescope time. He attempted to 
observe the comet on the mornings of 8-12 August 1982. Despite equipment problems 
that plagued observations on 8 and 9 August, the last three days yielded normal 
performance. On the last day, 12 August, the analyzing bandwidth was doubled from 380 
to 760 hz, with a corresponding increase in the frequency resolution, in order to widen 
the search window. They computed an ephemeris after the experiment, using all the astro- 
metric observations available for Comet Austin between June 1982 and November 1982. 
That ephemeris turned out to be substantially different from the ephemeris used during 
the actual radar observations. Despite correcting for this, and despite the distance from 
Earth being very similar to that of Comets Encke and Grigg-Skjellerup, five days of obser- 
vations in August 1982 did not result in a successful detection. 55 

Radar detections of comets were obviously fairly difficult to make, even with the best 
radar telescope then available. Another opportunity to attempt a newly-discovered comet 
came later that year. Comet Churyumov-Gerasimenko was discovered on a photograph 
taken on 11 September 1969 at the Alma-Ata observatory in the Soviet Union by K. I. 
Churyumov and S. I. Gerasimenko. At the time of Kamoun's radar observations in 
November 1982, Comet Churyumov-Gerasimenko was 0.39 astronomical units from 
Earth. It ought to have been detectable by the Arecibo radar. Kamoun attempted Comet 
Churyumov-Gerasimenko for 33 hours between 7 and 16 November 1982. Serious tech- 
nical problems on 7 and 16 November prevented acquisition of data. Further difficulties 
on 8 and 1 1 November caused loss of some data. In the end, the attempt on Comet 
Churyumov-Gerasimenko was not successful. 56 

From his successful and unsuccessful observations of comets, Kamoun estimated the 
radii of their nuclei, which were 0.4-3.6 km for Encke, 0.4-2.2 km for Grigg-Skjellerup, 



54. Kamoun, pp. 90 and 85; NAIC QR Q2/ 1982, 7-8. 

55. Kamoun, pp. 108-110; NAIC QR Q3/1982, 8. 

56. Kamoun, pp. 21 and 122; NAIC QR Q4/1982, 7-8; K. I. Churyumov and S. I. Gerasimenko, "Physical 
Observations of the Short-Period Comet 1969 IV," in G. A. Chebotarev, E. I. Kazimirchak-Polonskaya, and Brian 
G. Marsden, eds., The Motion, Evolution of Orbits, and Origin of Comets IAU Symposium 45 (New York: Springer- 
Verlag, 1972), pp. 27-34. Both Churyumov and Gerasimenko were in the Department of Astronomy, University 
of Kiev. 



218 



TO SEE THE UNSEEN 



less then 1.5 km for Austin, and less than 2 km for Churyumov-Gerasimenko. He also 
placed upper limits on the number of millimeter and centimeter-sized particles in the 
coma of the four comets (Table 7) . 57 





Table 7 
Upper Limits on the Number of Grains in the Coma of Four Comets 




Comet 


Grain-Size 


Assumed 
Ice 


Grain 
Olivine 


Composition 
Magnetite 
Iron Sulfide 


Encke 


mm 

cm 


4.5 10" 
1.5 10" 


1.5 10" 
6 10' 


7.5 10 16 
3 10' 




Grigg-Skjellerup 
and Austin 


mm 
cm 


3 10" 
10" 


10 16 
4.5 10' 


10 16 
2 10 10 






Churyumov- 
Gerasimenko 


mm 
cm 


6 10" 
2 10" 


2 10" 
9 10' 


10" 
4 10' 







In setting forth a program of future cometary radar studies, Kamoun noted that the 
comets attempted in his dissertation could not be observed again during the next 10 
years. Despite the scheduled reappearances of Encke in 1984 and 1987, of Grigg- 
Skjellerup in 1987, and of Churyumov-Gerasimenko in 1989, none of the comets would 
approach close enough for radar observation. On the other hand, he calculated, even if 
no improvement in radar sensitivity occurred, other comets would be accessible, 
particularly Comets Haneda-Campos (1984), Giacobini-Zinner (1985), Borelly and 
Denning-Fujikawa (1987), and Brorsen-Metcalf and Dubiago (1989). 58 None of those 
comets, however, was ever observed by radar. 

Instead, opportunities, in fact far better opportunities, came from comets never 
before seen. In early May 1983, as Paul Kamoun was writing his dissertation, preparations 
were underway at Arecibo to observe Comet IRAS-Araki-Alcock. On 25 April 1983, the 
Infrared Astronomical Satellite (IRAS) discovered Comet IRAS-Araki-Alcock. Initially, sci- 
entists believed it was an asteroid. In either case, it was sure to approach near the Earth. 
Astronomers calculated that the object would pass Earth at a distance of only 0.03 
astronomical units (450,000 km), that is, about 10 times closer than any other comet that 
Kamoun had observed for his dissertation. In fact, such a close approach for a comet had 
not been known to have occurred in more than two hundred years. Although Kamoun 
had pioneered cometary radar, he would miss the most spectacular cometary opportuni- 
ty. After writing up his thesis, he returned to France and took a position with a French 
aerospace firm. 59 

But observing Comet IRAS-Araki-Alcock was not going to be easy. Its orbit was high- 
ly inclined relative to the Earth's equator, and to make observation at Arecibo that much 
harder, as Don Campbell explained, "It was moving in declination so rapidly, that it 
actually went through the entire sky coverage of Arecibo in one day. We had a two-and-a- 
half-hour observing window, and that was it!" 60 



57. Kamoun, p. 230. 

58. Kamoun, p. 237. 

59. Campbell 9 December 1993; Kamoun, p. 238; Jurgens, "Seeing Comet IRAS," p. 221; information 
supplied by Pettengill. 

60. Campbell 9 December 1993. 



THE OUTER LIMITS 2 1 9 



The ability to get good data on Comet IRAS-Araki-Alcock depended heavily on hav- 
ing an accurate ephemeris. That was the job of Brian Marsden and Irwin Shapiro, who 
had just become Director of the Harvard-Smithsonian Astrophysical Observatory in 
January 1983, four months before the comet's discovery. 'Taking over this place was an 
all-consuming job," he recalled. "I worked day and night.' But for a few days, I dropped this 
job like a ton of bricks, literally, to develop the ephemeris needed to observe IRAS- 
Araki-Alcock at Arecibo and Goldstone." 61 

Working closely with Brian Marsden, Shapiro generated an ephemeris for the comet. 
"It was a big mess," Shapiro explained. "I was up until 2:30 in the morning every night. 
The difficulty was due to there being very few comet observations, mostly bad. We had to 
try numerous combinations to sort the good from the bad." Then Shapiro turned to the 
task of preparing an ephemeris for the radar. 'The radar ephemeris was prepared at 
Lincoln Laboratory; the radar observations were to be made at Arecibo. It was a logistical 
nightmare, because of the incredible time pressure," Shapiro explained. "As the time of 
close approach of the comet to Arecibo neared, we sent the ephemeris electronically. It 
arrived an hour before the comet was to make its one and only pass over head. It worked 
brilliantly." 62 

Don Campbell took high quality data on IRAS-Araki-Alcock for about three hours 
during the single observation evening of 1 1 May when the comet was in the telescope's 
declination window. Campbell recalled: "We got extremely nice data. You could actually 
see the echo on the oscilloscope right there in the control room. It was all over the place. 
A nice sine wave popping in and out. It was all very exciting. We measured only spectra 
and obtained a lot of very interesting data on IRAS-Araki-Alcock in just that two-hour 
period." 63 

More surprising than a powerful echo from a relatively large nucleus, the spectra 
showed a broad low-level skirt distinct from the nucleus echo. The skirt suggested the 
possible existence of a cloud of unexpectedly large, centimeter-sized ejected particles 
from the comet. The IRAS-Araki-Alcock skirt spectrum appeared to be consistent with a 
model in which large grains were ejected from the nucleus by the same gas-drag mecha- 
nism used to explain the ejection of the smaller particles making up the dust coma and 
tail. 64 'This was the first time that such particles had ever been discovered," Campbell 
explained. "It made the whole experiment much more interesting." 65 

At the same time, Dick Goldstein and Rayjurgens, in collaboration with JPL comet 
specialist Zdenek Sekanina, prepared to look at IRAS-Araki-Alcock with the Goldstone 
radar. Previously, they had made failed attempts at Comets d'Arrest (1976), Kohoutek 
(1974), and Bradfield (1974). 66 IRAS-Araki-Alcock would be their first successful 
cometary detection. Their chief obstacle was the resuscitation the Goldstone radar. As 
Jurgens wrote: "As luck would have it, the JPL radar system had been shut down following 



61. Shapiro 1 October 1993. 

62. Shapiro 1 October 1993. 

63. Campbell 9 December 1993; Harmon, Campbell, Hine, Shapiro, and Marsden, "Radar Observations 
of Comet IRAS-Araki-Alcock 1983d," The Astrophysical Journal 338 (1989): 1071; Harmon, Campbell, Hine, 
Shapiro, and Marsden, Radar Observations of Comet IRAS-Araki-Alcock (1983d) Report 245 (Ithaca: NAIC. 
September 1988), Pettengill materials. 

64. Campbell 9 December 1993; NAIC QR Q2/1983, 7; Harmon, Campbell, Hine, Shapiro, and 
Marsden, "Radar Observations of Comet IRAS-Araki-Alcock 1983d," The Astrophysical Journal 338 (1989): 1071- 
1093; Campbell, Harmon, Hine, Shapiro, Marsden, and Pettengill, "Arecibo Radar Observations of Comets 
IRAS-Araki-Alcock and Sugano-Saigusa-Fujikawa," Bulletin of the American Astronomical Society 15 (1983): 800; 
Goldstein, Jurgens, and Zdenek Sekanina, "A Radar Study of Comet IRAS-Araki-Alcock 1983d," The Astronomical 
Journal^ (1984): 1745-1754; and Shapiro, Marsden, Whipple, Campbell, Harmon, and Hine, "Interpretations 
of Radar Observations of Comets," Bulletin of the American Astronomical Society 15 (1983): 800. 

65. Campbell 9 December 1993. 

66. Jurgens, "Seeing Comet IRAS," p. 221; Goldstein, Jurgens, and Sekanina, pp. 1745-1754. 



220 TO SEE THE UNSEEN 



the unsuccessful tracks of asteroid 4 Vesta on 28 May 1982. Since the radar system has seen 
only sporadic usage over the past few years, the X-band transmitter, the 20 year old 
computer and the data acquisition equipment were unreliable. We were in the midst of a 
major rebuilding project that would not be put into operation until March 1985. 
Fortunately, we had not removed the old equipment." 67 

Jurgens and a team of JPL engineers refurbished the radar equipment, while Mike 
Keesey prepared a radar ephemeris based on orbital elements supplied by Brian Marsden 
and Irwin Shapiro, who also had supplied the Arecibo ephemeris. The Goldstone obser- 
vations took place on 11 and 14 May 1982 at both S-band and X-band. On a few runs, 
echoes were received in the same circular polarization. 68 Goldstein, Jurgens, and Sekanina 
concluded that the nucleus of Comet IRAS-Araki-Alcock was very rough on a scale larger 
than the radar wavelength. They did not believe that the predominant backscattering 
mechanism was similar to that observed from the icy surfaces of the Galilean satellites, but 
instead consisted of single reflections from very rough surfaces. They posited, further- 
more, that the shape of the nucleus appeared to be irregular. Jurgens believed that the 
nucleus's shape could be represented fairly well by a triaxial ellipsoid having equatorial 
radii in a ratio of two to one. The JPL radar astronomers estimated its radius to be between 
three and six km (larger than any comet observed by Ramoun) and its rotational period 
to be from one to two days. 

Because of Jurgens' interest in asteroids, he and his JPL colleagues compared the 
comet to known asteroids. 'The observed spectral shapes are typical of those measured for 
small Earth-crossing asteroids except for the broadband skirt," they noted. "Due to dis- 
tance and sensitivity limitations, such a skirt would not have been detected on any aster- 
oid observed so far even if it existed." 69 However, they did not carry out a detailed analy- 
sis of the skirt. 

Within weeks after Comet IRAS-Araki-Alcock, another new comet, Sugano-Saigusa- 
Fujikawa, passed the Earth. The two comets coming so closely together created a "once in 
a lifetime" opportunity. Comet Sugano-Saigusa-Fujikawa came within 0.06 astronomical 
units of Earth in early June 1983. Don Campbell attempted Sugano-Saigusa-Fujikawa on 
the one day it was within the Arecibo telescope's declination window, while Jurgens and 
Goldstein tried during four full days of observations, which delayed the renovation of the 
Mars Station antenna for one month. "Night after night," Jurgens wrote, "we searched the 
sky in the area of the comet with no indication of an echo." 70 Arecibo, on the other hand, 
did find echoes; however, Sugano-Saigusa-Fujikawa was about three times further away 
than IRAS-Araki-Alcock had been, and it was a smaller comet, so that it was a less inter- 
esting and "somewhat disappointing" target. 71 

Despite the many unsuccessful and disappointing attempts to detect comets, until 
the passing of Comet Halley, only the radar observations of IRAS-Araki-Alcock made at 
Arecibo and Goldstone contributed to the vast amount of data collected by comet scien- 
tists at optical, radio, infrared, and ultraviolet wavelengths. 72 Comet Halley returns every 
76 years. Its reappearance prompted a global effort, the International Halley Watch, to 
coordinate ground and space observations. Unlike previous comets, Halley was investi- 
gated from a number of spacecraft sent by Japan (Suisei and Sakigake), the Soviet Union 
(Vega 1 and 2), and the European Space Agency (Giotto). The radar results, however, did 



67. Jurgens, "Seeing Comet IRAS," p. 222. 

68. Jurgens, "Seeing Comet IRAS," p. 222; Goldstein, Jurgens, and Sekanina, pp. 1745-1747. 

69. Goldstein, Jurgens, and Sekanina, p. 1754. 

70. Jurgens, "Seeing Comet IRAS," p. 224. 

71. Campbell 9 December 1993; NAIC QR Q2/1983, 7. 

72. Sekanina, "Nucleus of Comet IRAS-Araki-Alcock (1983 VII)," The Astronomical Journal 95 (1988): 
1876-1894. 



THE OUTER LIMITS 221 



not play a part in the international effort. 73 Radar was still a marginal tool for cometary 
research. 

Comet Halley was to make two close approaches to Earth during its appearance in 
1985-1986. At its closest approach in November 1985, it was to be 0.61 astronomical units 
from Earth, and during its second approach, even closer, 0.41 astronomical units, to Earth 
in April 1986. At the November 1985 approach, Halley would be visible at both Arecibo 
and Goldstone, though far below likely detectability at the latter site. Moreover, Halley was 
not within the Arecibo telescope's limited declination coverage during its closer approach 
to Earth in April 1986. 74 The chances for viewing Halley thus were small; the best chance 
was in November and December 1985, when Halley was to be 0.62 astronomical units dis- 
tant from Earth, not a good distance for observing comets. 

At Arecibo, John Harmon observed Halley on 24, 28, 29 November and 1 and 2 
December 1985 during its inbound Earth approach and detected a weak echo from Halley 
at a distance of 0.62 to 0.64 astronomical units, the most distant comet yet detected with 
radar. With the exception of IRAS-Araki-Alcock, comets observed earlier generally had 
been about 0.3 astronomical units away. A broadband feature with a high radar cross sec- 
tion and a large Doppler bandwidth dominated the echo spectrum, properties that were 
inconsistent with an echo from the nucleus. Halley, then, became the second comet to 
yield a radar detection of grains larger than two cm in radius ejected from the nucleus. 
Comet Halley also was the first radar bright comet observed; it had the largest radar cross 
section to date of any comet detected by radar. "If our interpretation of the echoes is 
correct," Don Campbell explained, "Halley is the first comet to give a stronger echo from 
particles than from the nucleus itself." 75 

The Arecibo attempt on Halley in 1985 was the last successful radar detection of a 
comet. In 1990, John Harmon attempted Comet Austin in cooperation with Steve Ostro, 
who tried to obtain echoes with the Goldstone X-band radar. Harmon also attempted 
Comet Honda-Mrkos-Pajddusakova in 1990, but again without success. 76 These failures 
only served to highlight the extreme difficulty of doing radar research on comets and, as 
a result, the lack of major radar contributions to cometary science. 

A Vision of Things to Come 

Asteroids did not make easy radar targets, either. Their small size and distance from 
Earth placed them at the limits of planetary radar capabilities. Also, the known popula- 
tion of asteroids outside the mainbelt between Mars and Jupiter, that is, the known 
number of asteroids that might approach Earth close enough for radar study, was far 
smaller than the quantity we know today. After the detection of Icarus at Haystack and 
Goldstone in June 1968, only six more asteroids came under radar investigation between 
then and July 1980: five near-Earth asteroids (1566 Icarus, 1685 Toro, 433 Eros, 1580 
Betulia, and Phocaea) and two mainbelt asteroids (1 Ceres and 4 Vesta). 



73. E. Griin, ed., "Halley and Giacobini-Zinner," Advances in Space Research vol. 5, no. 12 (1985): 1-344; 
J. W. Mason, ed., Comet Halley: Investigations, Results, Interpretations, 2 vols. (New York: Ellis Horwood, 1990); R. 
Reinhard and B. Battrick, eds., The Giotto Mission: Its Scientific Investigations (Noordwijk: ESTEC, European Space 
Agency, 1986); M. Grewing, F. Praderie, and R. Reinhard, eds., Exploration of Halley 's Comet (New York: Springer- 
Verlag, 1986). 

74. Kamoun, pp. 239-240; Campbell, Harmon, and Shapiro, "Radar Observations of Comet Halley, " The 
Astrophysical Journal 338 (1989): 1094-1105; Campbell, Harmon, and Shapiro, Radar Observations of Comet Halley 
Report 246 (Ithaca: NAIC, September 1988), Pettengill materials. 

75. Campbell 9 December 1993; Campbell, Harmon, and Shapiro, "Comet Halley," pp. 1094 and 1103; 
NAICQRQ4/1985.8. 

76. NAIC QR Q2/1990, 6. 



222 TO SEE THE UNSEEN 



Interest in asteroids was growing among astronomers during that 12-year period. 
Tom Gehrels, University of Arizona at Tucson, was the most vocal advocate of asteroid 
research. During the 1970s, he organized three asteroid conferences at Tucson which 
provided much of the impetus for the modern investigation of asteroids. He also 
initiated a program of asteroid detection called Spacewatch. Spacewatch, a survey 
telescope located on Kitt Peak to discover new asteroids, started operating in May 1963. 
Tom Gehrels also led an effort to use a modern CCD scanning camera on a specially 
designed telescope beginning in 1979. In its first two years, Spacewatch discovered 69 new 
asteroids. The rapid discovery rate of asteroids that started in the 1970s was due largely, 
however, to the Palomar Planet-Crossing Asteroid Survey (PCAS), begun in 1973 by 
Eleanor Helin and Eugene Shoemaker. The Survey initially used a 46-cm Schmidt camera 
to detect asteroids on the four to five nights each month around the new Moon. The 
exposed photographic plates were subjected to stereoscopic examination the same night 
they were taken, in case a new asteroid was recorded on the film. If an object were 
discovered, positional data was relayed by telephone to Brian Marsden at the Harvard- 
Smithsonian Astrophysical Center, where he headed a center for data on minor planets 
starting in 1978. Marsden then computed the orbit and ephemerides for further observa- 
tions. 

As a result of the Spacewatch and PCAS programs, the asteroid literature, as mea- 
sured by citations of asteroid papers, underwent the kind of swift growth that is typical of 
Big Science. 77 Although radar astronomers at first simply attempted to detect asteroids, 
both Arecibo and Goldstone investigators initiated systematic programs of asteroid detec- 
tion and research in the mid-seventies. The focus was on measuring radii, surface rough- 
ness, and composition, and on improving orbits. In addition, Ray Jurgens pioneered the 
modeling of asteroid shapes. 

Dick Goldstein, using the Goldstone Mars Station, obtained echoes from 1685 Toro, 
the first asteroid detected after Icarus, in 1972. After he combined the radar and optical 
data, Goldstein inferred that the asteroid had an irregular rocky surface slightly smoothed 
by a mantle of loose material. 78 The following asteroid opportunity, 433 Eros, arrived in 
January 1975. The experiment carried out on Eros at Goldstone was, in the words of Steve 
Ostro, 'The most important asteroid experiment before 1980," because data was taken at 
two frequencies (X-band and S-band) and in both senses of circular polarization. "As a 
result," according to Ostro, "they achieved the best characterization of an asteroid's cen- 
timeter-to-decimeter scale surface properties until the late 1980s. By then, all work was 
dual polarization. Jurgens and Goldstein were well ahead of their time." 79 

The data Goldstein and Jurgens collected indicated that the surface of Eros was 
much rougher than the Moon or any of the terrestrial planets. They described a surface 
completely covered with sharp edges, pits, subsurface holes, or embedded chunks. They 
also estimated the asteroid to have equatorial dimensions of 18.6 and 7.9 km. 80 In order 
to better describe the shape of Eros and other asteroids, Ray Jurgens developed a triaxial 
ellipsoid model. His work represented an important first step toward modeling asteroids 
with radar data. Optical observations often provide the spin rate and pole, prerequisite 
parameters for determining the shape of an asteroid from radar data. 81 



77. Clifford J. Cunningham, Introduction to Asteroids: The Next Frontier (Richmond: Willmann-Bell, 1988), 
pp. 2 and 97-101; Tom Gehrels, "The Asteroids: History, Surveys, Techniques, and Future Work," in Gehrels and 
Matthews, eds., Asteroids (Tucson: University of Arizona Press, 1979), pp. 4-5 and 13-14. 

78. Goldstein, D. B. Holdridge, and J. H. Lieske, "Minor Planets and Related Objects: 12. Radar 
Observations of (1685) Toro," The Astronomical Journal 78 (1973): 508-509. 

79. Ostro 25 May 1994. 

80. Goldstein and Jurgens, "Radar Observations at 3.5 and 12.6 cm Wavelength of Asteroid 433 Eros," 
Icarus 28 (1976): 1-15. 

81. Jurgens, "Radar Backscattering from a Rough Rotating Triaxial Ellipsoid with Applications to the 
Geodesy of Small Asteroids," Icarus 49 (1982): 97-108. 



THE OUTER LIMITS 



223 




Figure 35 

In order to model the nonspherical shape and numerous axes of rotation of asteroids, Rayjurgens designed a coordinate frame 
to describe asteroids as rotating triaxial ellipsoids. This was the first attempt to model asteroid shapes with radar data. 
(Courtesy of Jet Propulsion Laboratory.) 

Continuing his pursuit of radar asteroid research, Rayjurgens outlined an ambitious 
10-year program of asteroid opportunities in 1977. The program laid out the kinds of 
measurements that ground-based radars (both Goldstone and Arecibo) could make with 
currently available transmitter power and receiver sensitivity. Jurgens estimated that the 
number of detectable asteroids available for study over the following 10 years was 60. It 
took a few years longer to reach that number, however, for a variety of reasons. Jurgens 
also pointed out that astronomers could use the radar data in many cases to calculate the 
radius, average surface roughness, rotational rate, and polar axis direction, and in some 
cases the radar albedos and orbital parameters, of asteroids. 82 

In a memorandum to NASA Headquarters, Jurgens described the kinds of asteroid 
opportunities that would become available upon the upgrading of the Goldstone radar 
and argued for the scientific value of determining object size, rotation period, shape, and 
surface properties from range and Doppler measurements, in the hopes of funding 
asteroid radar research at JPL. 83 Jurgens had foreseen and mapped out the kind of radar 
asteroid research program that only a few years later would materialize, but at Arecibo. 
Jurgens' asteroid research program did not take root at JPL; the Goldstone radar was shut 
down after some unsuccessful tracks on Vesta on 28 May 1982. 84 In contrast, radar aster- 
oid studies at Arecibo were far more energetic. There, Brian Marsden worked with Irwin 
Shapiro, the guru of the Planetary Ephemeris Program, to undertake a systematic study 



82. Jurgens and D. F. Bender, "Radar Detectability of Asteroids: A Survey of Opportunities for 1977 
through 1987," Icarus 31 (1977): 483-497. The asteroid research program grew out of a larger work Jurgens did 
while at JPL, namely, Jurgens, A Survey of Ground-based Radar Astronomical Capability Employing 64 and 128 Meter 
Diameter Antenna Systems at S and X Band, Report 890-44 (Pasadena: JPL, March 1977). See also Pettengill and 
Jurgens, "Radar Observations of Asteroids," in Gehrels and Matthews, Asteroids, pp. 206-211. 

83. Jurgens to Geoffrey A. Briggs, 12 August 1982, Jurgens materials. 

84. Jurgens, "Seeing Comet IRAS," p. 222. 



224 TO SEE THE UNSEEN 



of asteroid astrometry and composition. 85 The first asteroid observations that formed part 
of that program were of Eros. 

In 1975, Don Campbell and Gordon Pettengill observed Eros with the old UHF (430- 
MHz; 70-cm) transmitter. That was the first asteroid detected by the Arecibo telescope 
radar. Campbell and Pettengill measured the radar cross section of the asteroid and esti- 
mated its radius to be about 16 km. They also found the surface of Eros to be rough com- 
pared to the surfaces of the terrestrial planets and the Moon. When Pettengill and 
Campbell attempted to determine the composition of the surface, they could only con- 
clude that it could not be a highly conductive metal. 86 

After unsuccessful attempts at asteroids Ceres and Metis, Pettengill and Marsden 
observed 1580 Betulia in 1976, the first asteroid target of the new S-band radar. Steve 
Ostro, then a graduate student at MIT, did the analysis. He measured the asteroid's aver- 
age radar cross section and set a lower limit to the asteroid's radius of 2.9 0.2 km. 87 

Pettengill and Ostro next turned their attention to the mainbelt asteroid Ceres. 
Already, in December 1975, Pettengill and Marsden, in collaboration with Goldstein (JPL) 
and Tom Gehrels and Benjamin Zellner (University of Arizona) had failed to obtain 
echoes from both Ceres and Metis, another mainbelt asteroid. The lack of an echo from 
Metis was not surprising, but Ceres should have been easy to detect; they interpreted the 
absence of an echo as indicating a smaller cross section than they had expected. 88 

Ostro, Pettengill, and Campbell finally detected Ceres with the Arecibo S-band radar 
in March and April 1977. This was the first mainbelt asteroid detected by radar. The 
greater sensitivity of the S-band instrument made it possible for the radar to reach into the 
mainbelt of asteroids and detect such a small body. The opportunity of March 1977 was 
slightly more favorable than that of 1975, thanks to the installation of a more sensitive line 
feed in 1976. Ceres was found to have a low radar cross section, less than that for the 
Moon, the terrestrial planets, and even Eros. On the other hand, the asteroid appeared to 
have a very rough surface at some scale comparable to, or larger than, the 12.6-cm wave- 
length of the radar, that is, rougher than the Moon and terrestrial planets, but smoother 
than the Galilean satellites of Jupiter. 89 

Noisy data taken on mainbelt asteroid Vesta during three,nights of observations in 
November 1979 returned only a weak detection. 90 Each asteroid detection seemed to 
bring a new revelation; no pattern emerged. Unlike the terrestrial planets, asteroids pre- 
sented not a few bodies to study but an entire population, a population, moreover, that 
the growing discovery rate kept increasing. Although the systems of Jupiter and Saturn 
defined the outer limits of planetary radar astronomy after 1975, the asteroids defined its 
future. They were on their way to deposing Venus from its position as the favored target 
of radar astronomers. 



85. NAIC QR Q2/ 1976, 6-7. 

86. Campbell, Pettengill, and Shapiro, "70-cm Radar Observations of 433 Eros," Icarus 28 (1976): 17-20; 
NAICQRQ1/1975, 4. 

87. Pettengill, Ostro, Shapiro, Marsden, and Campbell, "Radar Observations of Asteroid 1580 Betulia," 
Icarus 40 (1979): 350-354. 

88. NAIC QRQ4/ 1975, 5. 

89. Ostro, Pettengill, Shapiro, Campbell, and R. Green, "Radar Observations of Asteroid 1 Ceres," Icarus 
40 (1979): 355-358; NAIC QR Ql/1977, 6-7. 

90. Ostro, Campbell, Pettengill, and Shapiro, "Radar Detection of Vesta," Icarus 43 (1980): 169-171; 
Ostro 25/5/94; NAIC QR Q4/1979, 7. 



Chapter Nine 

One Step Beyond 



Just as the Arecibo S-band and the Goldstone X-band upgrades had propelled radar 
astronomy into new directions, in 1986 a second upgrade planned for the Arecibo radar 
and the restoration and upgrading of the Goldstone radar stimulated new shifts in the 
planetary radar paradigm. Instruments and hardware continued to drive the field. Fresh 
techniques, either developed by radar astronomers or borrowed from other fields, name- 
ly ionospheric and radio astronomy research, allowed radar astronomers to solve new 
problems on the terrestrial planets. Also, the bizarre radar signatures of the icy Galilean 
satellites appeared once again, though closer to home on the terrestrial planets, and sug- 
gested new problems to solve. 

The Goldstone Solar System Radar 

Planetary radar astronomy survived at JPL in a tenuous state as a testbed for DSN 
technology and as a mission-oriented activity. That state depended largely on support 
from specific upper-management individuals, Eb Rechtin and Walt Victor. After Rechtin 
left JPL and Victor transferred out of the Deep Space Network to the JPL Office of 
Planning and Review in December 1978, radar astronomy became vulnerable to extinc- 
tion. The DSN Advisory Group, headed by Rechtin, had judged that radar astronomy was 
no longer the testbed of DSN technology. 

The Goldstone radar was in desperate need of repair, and the old equipment had 
become very hard to maintain; few people knew how to work with it. By 1980, much of the 
equipment was old and not functioning properly. During experiments, for instance, entire 
runs of data would be flawed or lost as a result of computer malfunctions. "You simply had 
to bite the bullet and rebuild the whole damned thing, particularly the data acquisition 
systems," Ray Jurgens explained. 1 However, nobody wanted to pay the cost of the needed 
repairs and upgrades. 

Reviving the Goldstone radar so that planetary radar astronomy could once again 
prosper at JPL required that the activity have a new rationale. The initial arguments for 
funding needed new equipment focused on the value of radar to NASA flight missions 
and to planetary geology. In 1979, E. Myles Standish, Jr., who was in charge of the JPL 
planetary ephemeris program, wrote a memo to Richard R. Green, who had recently been 
promoted from the radar group to Advanced Systems, to explain that if no radar experi- 
ments were conducted, then the accuracy of the ephemerides for the terrestrial planets 
would suffer, and JPL would not be able to meet its ephemeris commitments to either the 
Galileo or Magellan missions. 2 

Obtaining mission approval had been a requisite for acquiring antenna time for 
radar experiments. As George Downs explained, "Dick Goldstein always wanted to 



1. Jurgens 23 May 1994. In addition to the computer and other hardware problems, small cracks 
appeared in the pedestal of the Goldstone Mars Station. The repair involved raising the 3,000-ton structure and 
replacing a large portion of the pedestal concrete. The antenna did not return to service until June 1984, after 
being down a year for repairs. JPL Annual Report, 1983, p. 26, and ibid., 1984, p. 26, JPLA. 

2. Memorandum, Standish to R. Green, 10 May 1979, Jurgens materials. 

225 



226 TO SEE THE UNSEEN 



connect us with a project. I believe he felt that if we tried to get constituency from geolo- 
gists alone, we wouldn't make it. Well, he was right." 3 In 1979, George Downs asked USGS 
geologist Henry J. Moore to write a letter in support of the Goldstone radar; Moore wrote 
to Arden L. Albee, Caltech professor of geology and the newJPL Chief Scientist. 

Albee was sympathetic and met with members of the JPL radar group, Ray Jurgens, 
George Downs, Stan Butman, and Rick Green, on 24 January 1980. As a result of the meet- 
ing, Albee wrote to the NASA Office of Space Science recommending a line item for radar 
astronomy in the fiscal 1982 budget. Thomas Mutch, associate administrator, NASA Office 
of Space Science, replied that he could not raise the annual allocation; the funding level 
would have to remain level. 4 

Some support for resurrection of the Goldstone radar could be counted on coming 
from the Planetary Radar Working Group, which consisted largely of geologists in the 
USGS and academia plus smaller numbers of individuals representing SAR remote sens- 
ing and NASA Headquarters, as well as radar astronomers Pettengill, Campbell, 
Goldstein, and Len Tyler. The Planetary Radar Working Group met in conjunction with 
the AAS Division for Planetary Sciences and the Lunar and Planetary Science Conference 
and discussed priorities in radar astronomy at Goldstone and Arecibo. Of course, the fate 
of the VOIR mission, not the Goldstone radar, was the focal point of discussions. 5 

With support from the Planetary Radar Working Group, Ray Jurgens and George 
Downs wrote a proposal requesting about $1.8 million to purchase a VAX computer to 
reduce radar data. They submitted it to the NASA planetary geology office because they 
thought planetary geologists would be the prime users of the data. In retrospect, George 
Downs judged that reviewers saw the proposal as a threat to their own funding and did not 
give it good reviews, while those who saw the project's usefulness gave it good reviews. 

Although Jurgens and Downs did not get the amount requested, the NASA Office of 
Space Science and Implementation did grant them enough to buy a new VAX-700 and 
about $150,000 a year to analyze radar data. Radar astronomy also achieved a modest level 
of recognition in 1982. The original 1971 NASA Management Instruction governing 
ground radio science, now considered obsolete, replaced the term "radio science" with 
"Radio and Radar Astronomy." Such was the state of radar astronomy when Downs left in 
1982. 6 

In 1983, radar astronomy acquired a new advocate, Nicholas A. Renzetti. Originally 
a DSN manager responsible for the interface between the DSN and its flight customers, 
starting in 1975 with the Viking and Voyager launches, Renzetti gave less attention to 
flight projects and more attention to applications of radio technology to non-flight pro- 
jects, such as geodynamics, the Search for Extraterrestrial Intelligence, radio astronomy, 
and starting in 1983, radar astronomy. Renzetti took on the task of convincing the Office 
of Space Science and other NASA Headquarters departments that it was in NASA's inter- 
est to support the Goldstone radar as a scientific instrument. 7 

The new rationale for funding the Goldstone radar, as defined by Renzetti, would be 
its use as a scientific instrument. In his campaign to garner support for the Goldstone 
radar, Renzetti was assisted by Steve Ostro, who took a position at JPL in late 1984, after 
leaving Cornell. They negotiated a new task in December 1987, in which the Goldstone 
radar would be treated as if it were a facility, not as a science task, with an annual budget 



3. Downs 4 October 1994. 

4. Henry J. Moore to Arden L. Albee, 2 July 1979, Jurgens materials; Memorandum, William H. Bayley 
to Murray, 4 February 1980, 91/7/89-13, JPLA; Various documents in "NASA Correspondence, 1980-1981," 
JPLPLC. 

5. Jurgens 23 May 1994; Planetary Radar Working Group mailing list, Jurgens materials; 
Memorandum, Carl W.Johnson to Murray, 27 October 1980, 99/8/89-13, JPLA. 

6. Jurgens 23 May 1994; Downs 4 October 1994; C. H. Terhune, Jr., to B. I. Edelson and R. E. Smylie, 
20 September 1982, "Chron 1982, #2," JPLPLC. 

7. Renzetti 16 April 1992; Renzetti 17 April 1992. 



ONE STEP BEYOND 227 



of about $200,000 for hardware improvements. The NASA task underwrote the interface 
between the DSN and the radar astronomers. The objective of the new task, called the 
Goldstone Solar System Radar (GSSR), was to support planning, experiment design, and 
coordination of data acquisition and engineering activities for all Goldstone planetary 
radar astronomy. As Steve Ostro explained, 'This has been the financial backbone for the 
Goldstone radar, and it is separate from the DSN." 8 

At the same time, Renzetti created a part-time position, the Friend of the Radar. The 
holder of that position was to carry out a number of duties, including NASA flight project 
science and liaisons with Arecibo Observatory, but most importantly interfacing with the 
scientific community. Tommy Thompson performed those duties until he became 
Magellan Science Manager in 1988, when Martin A. Slade replaced him. Slade had been 
a graduate student of Irwin Shapiro at MIT and had had some exposure to radar astron- 
omy during summer jobs at Haystack. His main previous research interests, however, lay 
elsewhere. 9 

The creation of the GSSR task and the Friend of the Radar were only first steps in 
addressing the core issue of funding the Goldstone radar on the basis of its use as a sci- 
entific instrument. Renzetti took tentative, unsuccessful steps to open up the Goldstone 
radar to outside researchers in order to operate it as a national research facility. He 
approached Von Eshleman and two others from outside JPL to propose radar experiments 
at Goldstone. Renzetti also proposed to Tor Hagfors, NAIC director, that a single peer 
review panel assess radar experiment proposals for both the GSSR (as the Goldstone Mars 
Station or DSS-14 now came to be called) and Arecibo. Moreover, hoping to acquire a 
facility budget for GSSR on a level with that of Arecibo, Renzetti proposed to Hagfors that 
Arecibo and GSSR present a common front to NASA, rather than appear as competing 
facilities. 10 

But it did not make sense to pursue the common budget, Renzetti reasoned, as long 
as the GSSR was not a national facility. The annual amount requested from NASA to make 
the GSSR a "first-class scientific instrument," $500,000, was not well received at NASA 
Headquarters. In comparison, the NASA budget for the Arecibo radar was only $362,000 
in 1986. 11 Nonetheless, Renzetti, who felt there was a built-in bias in favor of Arecibo at 
high-level NASA meetings, submitted a formal proposal to make the GSSR a national facil- 
ity, but it never got off the ground. 12 

A chief critic of the proposal to turn the Goldstone radar into a national research 
center was Dewey Muhleman of Caltech. He called parts of the proposal "ludicrous" and 
declared that it would do "nothing for Science, the Nation, NASA nor, in the long run, 
JPL." Moreover, he pointed out, the heavy scheduling of the antenna for spacecraft work 
militated against the plan. "I strongly favor," he wrote, "the idea of getting Radar 
Astronomy at JPL out of the closet of component development and into the light of pure 
science." 13 

Gradually, that was starting to take place. During a JPL administrative reorganization 
in the fall of 1987, the Office of Space Science and Instruments (OSSI) was created with 
Charles Elachi as its head. Elachi was a seasoned radar engineer with decades of SAR 
experience. After he obtained a modest level of funding, $150,000, from NASA 
Headquarters, Elachi named Steve Ostro manager of Planetary Radar Science and autho- 
rized him to allocate the funding. 14 



8. Ostro 18 May 1994; GSSR Min. 6 December 1984. 

9. Thompson 29 November 1994; Slade 24 May 1994; GSSR Min. 6 December 1984 and 31 March 
1988. 

10. GSSR Min. 29 December 1986. 

11. GSSR Min. 22 January 1987 and 26 February 1987; NAIC QR Ql/1986, 19. 

12. GSSR Min. 26 February 1987. 

13. Memorandum, Muhleman to Edward C. Posner, 28 October 1986, Ostro materials. 

14. GSSR Min. 3 December 1987, 14 January 1988, 18 February 1988, and 28 April 1988. 



228 TO SEE THE UNSEEN 



"At that point," Ostro explained, "I had a little bit of authority. I had the program 
office backing me. I acted as somewhat of a filter on proposals and papers, when I could, 
and I acted as the voice of science for radar." Ostro agreed with Muhleman's perception 
that JPL placed too much emphasis on hardware and not enough on doing science. The 
science community in general, he pointed out, viewed the GSSR as state-of-the-art elec- 
tronics, but saw Arecibo as producing state-of-the-art planetary radar data. The objective, 
Ostro declared in 1988, "is, a year from now, to have a sparkling list of GSSR radar articles 
that have appeared in high-quality journals." 15 Despite such sterling intentions on the part 
of Ostro and Renzetti, keeping JPL, DSN, and NASA management aware of the Goldstone 
radar's scientific achievements and potential has been a Sisyphean task. In contrast, the 
value of radar astronomy was established from the outset at the Arecibo Observatory. 

Here was an important difference between the two facilities that had a profound 
impact on the development of radar astronomy at each site. Even more important, how- 
ever, was the fact that Arecibo had acknowledged and formalized the existence of radar 
astronomy from the start; whereas JPL purposely had denied radar astronomy any formal 
existence. The difference has had long-term implications that has favored radar astrono- 
my science at Arecibo, while holding it back at JPL. 

New hardware and fresh leadership enabled radar astronomers to make new discov- 
eries about Mars, Mercury, and the asteroids with the Goldstone radar. The major 
hardware upgrade did not arise from a concerted campaign on the part of Renzetti and 
Ostro to improve the state of radar astronomy at JPL, but rather, in a fashion typical of the 
history of planetary radar astronomy, came from outside radar astronomy, namely, the 
Voyager mission to the outer planets. 

The Voyager upgrade of the main GSSR antenna, known within the Deep Space 
Network as DSS-14, involved enlarging the dish diameter from 64 (210 ft) to 70 meters 
(230 ft), increasing the surface accuracy, and improving the receiving system. These 
measures increased the sensitivity of the DSS-14 significantly. Tracking and acquiring data 
from the Voyager spacecraft, as they encountered Uranus and Neptune, stretched the 
capacity of the Deep Space Network. During the Neptune encounter, the Voyager X-band 
radio signal would be less than one-tenth as strong as during the Jupiter encounter in 
1979 and less than one-half as strong as during the Uranus encounter in 1986. 

A study to enlarge all the DSN 64-meter antennas to 70 meters already had been 
undertaken as early as 1973 in preparation for Voyager when it was still called Mariner 
Jupiter/Saturn. After completion of design work in 1984, the upgrade of the DSS-14 
began in October 1987 and concluded in May 1988. 16 When Steve Ostro arrived at JPL in 
1984, the DSS-14 lacked the threshold of sensitivity to do meaningful asteroid research. 
Upon completion of the initial upgrade phase, however, Ostro made his first successful 
asteroid observations with the DSS-14 in May 1986, when he detected echoes from 1986 
JK, an asteroid only just then discovered by Eugene and Carolyn Shoemaker. 

The Voyager upgrade had a profound impact on the practice of radar astronomy at 
JPL; it provided the GSSR the sensitivity needed to carry out research on a whole new set 
of targets (and to begin solving new sets of problems). Not only did the GSSR gain the 
ability to undertake significant asteroid research, but when linked to the Very Large Array 
in New Mexico, as we shall see later, it became a new radar research tool. 

Despite these major upgrades, the GSSR had serious problems as a scientific instru- 
ment. The site lacked dormitory and cooking facilities for visiting or even JPL scientists, 
and the drive to Barstow 50 miles away on winding roads after a night of observations was 
dangerous. These deficiencies and dangers persist today. Furthermore, the radar itself was 
far from user-friendly. "It was just impossible to work," Ostro explained. "For example, the 



15. Ostro 18 May 1994; GSSR Min. 14 January 1988 and 18 February 1988. 

16. JPL Annual Report, 1973-1974, p. 15; ibid., 1984, p. 13; ibid., 1987, p. 41; and ibid., 1988, p. 28, 
JPLA. 



ONE STEP BEYOND 229 



VAX that is used for data acquisition at Goldstone is not good for radar astronomy for 
various technical reasons. It has been improved a lot since the mid-1980s, but even now it 
is difficult, for example, to stamp your data with a high-precision UTC [from the French 
for Coordinated Universal Time] time tag. For this kind of work, the first thing you need 
on your data is a UTC time tag." 17 

The Arecibo Observatory stood in sharp contrast to the Goldstone radar. It had 
proper quarters for visiting scientists, and the radar was far more user-friendly. Moreover, 
in 1986, the Arecibo Observatory proposed a major upgrade of the radar that would 
benefit both ionospheric and radio astronomy research and planetary radar astronomy. 
The Arecibo upgrade stirred Renzetti to seek funding for a Goldstone radar upgrade. 

Renzetti lobbied the DSN and NASA hierarchy for funding for a Goldstone one- 
megawatt transmitter, which JPL engineers initially estimated would cost $12 million. A 
good argument for DSN use of the radar would not fly; the rationale had to be its use for 
scientific research, Renzetti realized. The radar upgrade, to be completed in fiscal year 
1993 and costing $10 million over two years, appeared in the DSN budget for fiscal 1989. 
JPL viewed the price tag as "pared to the bone." In the end, Congress approved the expen- 
diture not as a specific radar upgrade but as an ambiguous improvement of the DSN. This 
ambiguity freed DSN management to use the radar transmitter money to purchase low- 
noise supercooled masers to improve antenna sensitivity for Galileo's encounter with Io. 18 

It was not clear, moreover, that radar science at JPL needed the one-megawatt trans- 
mitter. The estimated cost of the transmitter now stood at $16 million. Steve Ostro 
believed that if the cost were reduced below $8 million, the improved science capacity 
would justify the expense. The high cost reflected JPL administrative and DSN operational 
support requirements that added several million dollars to the cost. 19 

Ostro favored upgrading the GSSR antenna's subreflector to improve its ability to 
make asteroid observations. The long time needed to rotate the subreflector, which was 
never designed to act as a transmit/receive switch, compromised short round-trip-time 
asteroid observations. 'The most powerful scientific rationale for the longterm support of 
GSSR," Ostro argued, was work on near-Earth asteroids. The estimated price tag for the 
transmit/receive upgrade, which involved turning the transmit-only horn into a horn 
capable of switching quickly back and forth between transmit and receive, was $485,000. 20 

Instead of going directly through the DSN hierarchy for a radar upgrade, Renzetti 
changed his strategy. The one-megawatt transmitter and two other radar improvements 
(construction of a transmit/receive horn and modernization of the data acquisition 
system) were submitted to a panel of outside scientists for review. Gordon Pettengill 
chaired the Goldstone Planetary Radar Science Review Committee, as the panel was 
called. It included planetary astronomers and geologists, as well as Don Campbell and Tor 
Hagfors from the Arecibo Observatory. 21 



17. Ostro 18 May 1994. 

18. GSSR Min. 22 January 1987, 18 June 1987, 23 July 1987, 24 September 1987, 18 February 1988, 
31 March 1988, and 26 April 1990; Renzetti, Thompson, and Slade, "Relative Planetary Radar Sensitivities: 
Arecibo and Goldstone," TDA Progress Report 42-94 (Pasadena: JPL, April-June 1988), pp. 287-293; Arthur J. 
Freiley, Bruce L. Conroy, Daniel J. Hoppe, and Alaudin M. Bhanji, "Design Concepts of a 1-MW CW X-Band 
Transmit/Receive System for Planetary Radar," IEEE Transactions on Microwave Theory and Techniqiies 40 (1992): 
1047-1055. 

19. GSSR Min. 6 February 1992. 

20. Memorandum, Ostro to Elachi, 29 August 1990; Memorandum, David Hills to Dick Mathison, 1 
October 1990; Memorandum, Ostro to Larry N. Dumas, 15 October 1990, Ostro materials. 

21. Pettengill to Elachi, 22 August 1991, and attachments, Ostro materials. The members of the 
Goldstone Planetary Radar Science Review Committee were Gordon H. Pettengill, MIT; Michael J. S. Belton, Kitt 
Peak National Observatory; Donald B. Campbell, NAIC; Clark R. Chapman, Planetary Science Institute; Tor 
Hagfors, NAIC; Bruce W. Hapke, University of Pittsburgh; Randolph L. Kirk, USGS; David Morrison, NASA 
Ames Research Center; and F. Peter Schloerb, University of Massachusetts. 



230 TO SEE THE UNSEEN 



Although invited to join the Committee, Muhleman declined. He "took the attitude, 
well, this is one more panel, it can't be that important. How about if I don't come? Let me 
know how it comes out. That was a terrible mistake. It really was.. ..The JPL viewpoint was 
not represented." 22 More importantly for Muhleman, his viewpoint was not represented, 
and he paid the price. The Committee met on 8 August 1991 and presented its conclu- 
sions later that month. The Committee applauded "the efforts currently underway by JPL 
management to broaden the usage of the Goldstone facilities (including observations 
jointly with the VLA) to include members of the larger North American and global plan- 
etary communities." 

Of the three improvements, the committee gave the highest priority to the single- 
horn, fast-transmit/receive-switchover system. That improvement would serve asteroid 
work only. "At a lower, but still high, priority," the committee endorsed the modernization 
of the data acquisition system and recommended that the output protocols and formats 
of the new system be coordinated with those of the Arecibo planetary radar. Each of these 
two improvements had a modest cost of about $500,000 spread over one to two years. 

The one-megawatt transmitter, the committee judged, "seems less attractive as an 
upgrading option than the first two presented." The cost was too high for the amount of 
sensitivity gained. The value of the transmitter upgrade, the committee decided, lay in 
observing Titan, "but we do not find the scientific argument compelling for what appears 
to be a fairly narrowly focused study of a single object. We note also that the improved 
transmitter is unlikely to be available in time to provide data that materially assist in the 
design of the Cassini Mission." 23 

Titan, however, was of the highest research interest to Dewey Muhleman. "In my 
absence," he complained, "this panel frankly wrote a silly report. It just really made me 
sick to read it. It said that the only advantage of going to a megawatt on the Goldstone 
antenna was to be able to do Titan better with the VLA. Nothing else was really important. 
That is ridiculous. For everything we do, our integration time would be cut down by a fac- 
tor of four by doubling our power to a megawatt. We would be able to do much more on 
each one of these objects and quite frankly continue to rival Arecibo after the upgrade." 24 

The Arecibo Upgrade 

The struggle at JPL to gain recognition for the GSSR as a scientific instrument stood 
in stark contrast to the effort to upgrade the Arecibo telescope. Both NASA and the NSF 
already recognized Arecibo as a national research center, and the rationale for any 
upgrade would be on the basis of scientific need. Furthermore, the Arecibo upgrade stood 
to benefit all research at the facility, radio and radar astronomy and ionospheric research, 
not just planetary radar astronomy. Other factors eased the process of garnering support 
for the Arecibo upgrade, including the method of funding what was, in relative terms, a 
low-cost project. 

The Arecibo upgrade was a package of five interrelated improvements: 1) installa- 
tion of a ground screen to virtually eliminate noise from the surrounding earth; 2) 
adjustment of the reflector surface to enhance antenna gain; 3) correction of the 
pointing system; 4) replacement of the accumulation of radio astronomy line feeds with a 
single reflector feed possessing large bandwidth, low loss, high gain, and continuous 
frequency coverage from 300 MHz (1 meter) to 8 GHz (3.75 cm); and 5) doubling the 
S-band transmitter power to one megawatt. The total effect of these changes was to 



22. Muhleman 27 May 1994. 

23. Pettengill to Elachi, 22 August 1991, and attachments, Ostro materials. 

24. Muhleman 27 May 1994. 



ONE STEP BEYOND 231 



increase radar sensitivity by a factor of 10 to 50 (about 20 times on average), to double its 
range or to detect objects 10 times smaller than previously possible. 25 

The principal objective of the upgrade, however, was to solve a problem that had 
plagued the telescope since its creation the problem of spherical aberration. Unlike 
parabolic dishes, the Arecibo spherical antenna did not focus waves in a single point. The 
antenna feed system designed by the Air Force did not work efficiently, and though later 
feeds improved the telescope's performance, they did not perform up to the level of a 
Gregorian reflector, the solution recognized as early as the 1960s. Named for the 
astronomer John Gregory, a Gregorian reflector is concave and placed above the prime 
focus of a telescope. In a Cassegrain system, the type used, for example, on the Goldstone 
DSS-14, the reflector is convex mounted below the prime focus. 26 

Designing the Gregorian optics was a daunting task. A Cornell graduate student had 
considered the use of Gregorian optics, an option also studied by the AFCRL's Antenna 
Laboratory. 27 Frank Drake, director of the NAIC from 1971 to 1981, nurtured the 
Gregorian reflector idea and attempted unsuccessfully to gain financial support to gather 
together the necessary antenna expertise to submit a formal proposal to the NSF. 28 

Design of the Gregorian reflector did not begin until 1984, after Tor Hagfors became 
director of the NAIC in late 1982. After serving earlier as director of the Arecibo 
Observatory following the departure of Gordon Pettengill, Hagfors spent a number of 
years in Scandinavia building the EISCAT facility, before returning to Cornell to head the 
NAIC.^ 

EISCAT (European Incoherent Scatter Association) is a European consortium 
headquartered at Kiruna, Sweden. Inaugurated by the King of Sweden in August 1981, the 
EISCAT facility is a high-power radar installed at sites in Norway and Finland for the study 
of the Earth's ionosphere, upper atmosphere, and magnetosphere at high latitudes. 
Germany, France, and the United Kingdom bore the greatest share of its construction 
costs (25 percent each), while Sweden (10 percent), Norway (10 percent), and Finland 
(5 percent) contributed the rest. 30 

Under the direction of Tor Hagfors, the NAIC initiated systematic studies of several 
major antenna upgrading projects in 1984. As part of the upgrading project, the NAIC 
concluded consulting agreements with a number of antenna experts. Among them were 
Alan Love, who had designed the telescope's first circular feed, and Sebastian von 
Hoerner. Morton S. Roberts, director of the National Radio Astronomy Observatory 
(NRAO), and a member of the Arecibo Advisory Board, suggested that the NAIC hire as 
a consultant von Hoerner, a well known antenna expert working for the NRAO. The 
project appealed to von Hoerner's imagination, and he set to work designing the 
Gregorian optics and laying out the initial description of the shape and size of the reflec- 
tor. He also realized the need for a tertiary reflector. 31 



25. Hagfors, The Arecibo Gregorian Upgrading," in Joseph H. Taylor and Michael M. Davis, eds., 
Scientific Benefits of an Upgraded Arecibo Telescope (Arecibo: NAIC, 1987) , p. 4, and Ostro, "Benefits of an Upgraded 
Arecibo Observatory for Radar Observations of Asteroids and Natural Satellites," in ibid., p. 233. 

26. Campbell 9 December 1993. 

27. Kay, A Line Source Feed, passim, and Pierluissi, A Theoretical Study of Gregorian Radio Telescopes, passim. 

28. Hagfors, The Arecibo Gregorian Upgrading," p. 3; Per-Simon Kildal, Lynn A. Baker, and Hagfors, 
The Arecibo Upgrading: Electrical Design and Expected Performance of the Dual-Reflector Feed System," 
Proceedings oftheIEEE82 (1994): 714. 

29. NAIC QR Q3/1982, 19; Campbell 7 December 1993; Campbell 9 December 1993. 

30. Lovell, The JodreU Bank Telescope, pp. 270-271. 

31. Campbell 9 December 1993; Hagfors, The Arecibo Gregorian Upgrading," p. 3. 



232 



TO SEE THE UNSEEN 



X 




Ring Beam 



Window" membrane 60" Dia. Slight Pressurization 



\ 



Figure 36 

Diagram illustrating Gregorian optics of the Arecibo upgrade subreflector. Unlike the Lincoln Laboratory radomes, this one is 
not designed to allow radio signals to penetrate the radome shell. (Courtesy of National Astronomy and Ionosphere Center, 
which is operated by Cornell University under contract with the National Science Foundation.) 

In addition, Hagfors brought in Per-Simon Kildal, a professor at Chalmers University 
of Technology, Gothenburg, Sweden. Kildal was an expert in the design of feed horns and 
antenna diffraction effects and a former student of Hagfors. He had performed some of 
the design work on the EISCAT antennas for his doctoral thesis. When Kildal worked for 
the NAIC for two months during the summer of 1984, he joined NAIC line feed designer 
Lynn A. Baker. Baker and Kildal devised a practical Gregorian design to correctly illumi- 
nate the primary reflector. 32 



32. Campbell 9 December 1993; NAIC QR Q2/ 1984, 14; Hagfors, The Arecibo Gregorian Upgrading," 
p. 3; Kildal, Baker, and Hagfors, p. 714. 



ONE STEP BEYOND 233 



Designing and installing the Gregorian reflector also changed the mechanical stress 
on the suspended platform. In order to work on the mechanical engineering aspects of 
the project, Hagfors asked Paul Stetson, an antenna builder formerly with Lincoln 
Laboratory, to come out of retirement. Stetson joined the NAIC in February 1984. 33 

As a test of the Gregorian feed concept, the NAIC at its own expense constructed and 
installed a so-called mini-gregorian antenna which was to illuminate a 107-meter (350-ft) 
diameter area of the reflector. Also, the ground screen underwent preliminary design, 
and another study determined that the dish surface could be adjusted to be operational 
up to 8 GHz (3.75 cm). 34 

In 1984, as these design studies were underway, the NAIC submitted a preliminary 
proposal to the National Science Foundation for Phase 1, the ground screen. The NAIC 
submitted the Phase 2 preliminary proposal in 1985 for the Gregorian reflector system, 
the new radar transmitter, ancillary receivers, and data processing equipment. The NAIC 
then entered into negotiations with both the NSF and NASA, the two NAIC funding agen- 
cies. The House subcommittee that handled NSF appropriations was well aware of the 
upgrade project. Jerome Bob Traxler (D-Mich.), the chairperson of the House subcom- 
mittee, Harry Block, the NSF director, and Dick Mallow, the subcommittee's chief of staff, 
visited Arecibo several times. 35 

The key to selling the project to the scientific community, which ultimately reviewed 
all NSF proposals, was the building of consensus, a standard strategy among American sci- 
entists. The NSF proposals were supposed to stand on their own merit. Whether those 
reviews were good or bad was critical to the success of the upgrade project. The keystone 
of consensus-building was a workshop held at Cornell University 13-15 October 1986. The 
NSF proposal for Phase 1 was already under review, when the workshop took place. Talks 
highlighted the kinds of scientific experiments one could do with the upgraded telescope, 
whether in atmospheric research or in radio astronomy. Steve Ostro, Don Campbell, and 
Irwin Shapiro pitched the possibilities for radar astronomy. 



33. NAIC QR Q2/1984, 14; Campbell 9 December 1993; Hagfors, "The Arecibo Gregorian Upgrading," 
p. 3. 

34. NAIC QR Q2/1984, 14, and Q3/1984, 15; Hagfors, The Arecibo Gregorian Upgrading," p. 4; 
Kildal, Baker, and Hagfors, pp. 717-718 and 722. 

35. Campbell 9 December 1993; Dickman 2 December 1992. 



234 



TO SEE THE UNSEEN 





Figure 37 

View of the, Arealm Observatory dish. The completed ground screen is visible in the background. (Courtesy of National 
Astronomy and Ionosphere Center, which is operated by Cornell University under contract with the National Science 
Foundation.) 

Ostro largely proposed research on mainbelt and near-Earth approaching asteroids, 
passing quickly over other solar system objects, such as the moons of Mars, Jupiter, and 
Saturn. Don Campbell emphasized exploration of the terrestrial planets and comets. The 
major impact of the upgrading, he and Shapiro acknowledged, would be on the observa- 
tion of asteroids. 36 The scientific repercussion of the Arecibo upgrade for radar astrono- 
my would be to sustain the observatory as the major research instrument and to make 
asteroid studies the predominant area of research. 

The NSF sent the NAIC upgrade proposals out for review. The reviews aided the NSF 
in prioritizing its spending. Where the project stood within the NSF's own priority list of 
projects also was subject to input from the Division of Astronomy, primarily, and from the 



36. Ostro, "Benefits of an Upgraded Arecibo," pp. 233-239; Campbell, "Prospects for Radar 
Observations of Comets and the Terrestrial Planets," in Taylor and Davis, pp. 243-248; Shapiro, "Radar Tests of 
Gravitational Theories and Other Exotica," in ibid., pp. 225-232. 



ONE STEP BEYOND 235 



Division of Atmospheric Sciences. Within NASA, the planetary program decided funding 
priorities. In 1988, following the Cornell workshop, the NAIC submitted the main pro- 
posal for the Gregorian system and radar transmitter. Numerous discussions, presenta- 
tions, committee meetings, and reviews followed. Also providing input was the Bahcall 
Committee, the successor to the Whitford Panel. 37 

The Bahcall Committee, named for its chair John N. Bahcall, Princeton Institute for 
Advanced Study, and formally known as the Astronomy and Astrophysics Survey 
Committee, was a group of 15 astronomers and astrophysicists commissioned in 1989 by 
the National Academy of Sciences to survey their fields and to recommend new ground 
and space programs for the coming decade. To carry out the actual work, the Committee 
established 15 advisory panels to represent different subdisciplines, and those panels sub- 
mitted their reports in June and July 1990. 38 

Radar astronomy came under the general umbrella of the Planetary Astronomy 
Panel, chaired by David Morrison, NASA Ames Research Center, chair, and Donald 
Hunten, University of Arizona, vice chair. Among the 22 planetary scientists constituting 
the panel was one radar astronomer, Steve Ostro. The Planetary Astronomy Panel recom- 
mended several facilities as "critically important" for planetary astronomy in the 1990s. 
Prioritized according to their cost (small, medium, large) within the categories "space- 
based" and "ground-based," the most important small ground facility for planetary astron- 
omy was the Arecibo upgrade. 39 

The upgrade was never regarded as a huge project. The total estimated price tag of 
the upgrade, around $23 million spread out over four years, placed it in the "small" cate- 
gory; even the medium-sized proposed facilities cost substantially more. The relatively 
small total amount underwent further diminution in such a way that the project was never 
big enough to be a separate line item within the budget of the Office of Management and 
Budget. Both NASA and the NSF split the total cost, which underwent further division 
within each agency, so that the total amount per year was never a huge sum for each agen- 
cy or for each agency program. 

Geoff Briggs, director of the Division of Solar System Exploration within the NASA 
Office of Space Science, chaired discussions about the project with the NAIC, NASA, and 
the NSF. According to Don Campbell, "Briggs somewhat arbitrarily just took it on himself 
to break up who was going to pay for what right there." 40 

The allocation of the costs of what was already considered a small, low-cost project 
was a strategy in tune with the budgetary times. NASA would pay 100 percent of the 
ground screen and the one-megawatt radar transmitter costs, but the money came from 
the budgets of three different divisions. The Division of Solar System Exploration paid for 
the ground screen; the Office of Space Communications paid for the transmitter; and the 
Division of Biological Sciences, the source of SETI (Search for Extra-Terrestrial 
Intelligence) funding, contributed partially to the Gregorian reflector. The NSF paid for 
the remainder, with the Division of Astronomical Sciences paying for some specific equip- 
ment. The distribution of individual program contributions split the cost evenly between 
the two agencies and became the basis for the memorandum of understanding between 
NASA and the NSF that covered the upgrade. 41 



37. Campbell 9 December 1993; Kildal, Baker, and Hagfors, p. 715. 

38. John Bahcall, "Preface," in National Research Council, The Decade of Discovery in Astronomy and 
Astrophysics (Washington: National Academy Press, 1991), pp. ix-xi. 

39. National Research Council, Working Papers: Astronomy and Astrof>hysics Panel Reports (Washington: 
National Academy Press, 1991), pp. X- l-X-20. 

40. Campbell 9 December 1993. 

41. Dickman 2 December 1992; Campbell 9 December 1993. 



236 TO SEE THE UNSEEN 



Titan 

The Arecibo upgrade, when completed, promises entirely new research capabilities 
that will open up a new set of targets to be explored and new problems to be solved. 
Another upgrade, though not intended to provide new radar capability, created a research 
instrument that never existed before. That was the Voyager upgrade. It involved improve- 
ment of the GSSR, as well as the Very Large Array (VLA) , a radio telescope located in New 
Mexico. For the VLA upgrade, NASA installed low-noise X-band receivers on each of the 
27 VLA antennas. When radar astronomers linked the Goldstone radar and the VLA in a 
bistatic mode, they created a radar with an extraordinary capacity for exploring the solar 
system. 

The upgrade of the VLA for the Voyager mission originated in the need to commu- 
nicate with the spacecraft at unprecedented distances. During Voyager's encounter with 
Neptune, its X-band radio signal would be less than one-tenth as strong as from Jupiter 
and less than one-half as strong as from Uranus. In addition to the enlargement of the 
DSN 64-meter antennas to 70 meters in diameter, the Neptune encounter required assis- 
tance from the Parkes telescope in Australia and the VLA. Through the radio astronomy 
technique of arraying, and the installation of low-noise receivers on each VLA dish, the 
echoes received from the VLA were combined with those received at the Goldstone 
70-meter and 34-meter dishes to provide a data rate more than double that which would 
have been available with Goldstone's antennas alone. 42 

The idea of using the VLA as a receiver in a bistatic radar system was not new; Ed 
Lilley had suggested some two decades earlier a bistatic radar consisting of the VLA and 
the NEROC transmitter for carrying out planetary radar mapping. 43 Moreover, the VLA 
management already had thought of the possibility of a Goldstone-VLA bistatic radar years 
earlier, when they were looking for a broader foundation of support for a facility strictly 
dedicated to radio astronomy. They, therefore, were receptive to the suggestion of Nick 
Renzetti (JPL) that joint Goldstone-VLA radar experiments be conducted, provided the 
proposed experiments first would undergo the normal review process. 44 

As the Goldstone and VLA upgrades were underway, Caltech professor Dewey 
Muhleman became interested in the possibilities opened up by a Goldstone-VLA bistatic 
radar. After abandoning a career in radar astronomy in 1966 as professor of planetary sci- 
ence at Caltech, Muhleman switched to the study of radio emissions from the planets. 
Muhleman thought the Goldstone-VLA radar an excellent tool for exploring Saturn's 
barely explored and poorly understood moon, Titan. Scientists knew nothing about 
Titan's surface, because like the surface of Venus, it is hidden by an opaque cloud cover. 45 

Despite, or perhaps because of, this lack of knowledge, scientists speculated on the 
nature of the satellite's surface. According to conventional wisdom, Titan's surface was an 
ocean of ethane and methane, which would have almost no reflecting surface at radar 
wavelengths. 46 In 1980, Voyager 1 flew past Titan and provided fresh facts about the 
moon's surface temperature (about 94 Kelvin) and surface pressure (around 1,500 mil- 
libars) . Voyager found an atmosphere composed mainly of nitrogen and trace amounts of 



42. Murray to Morton S. Roberts, 25 February 1982, "Chiron 1982 #1," and Memorandum, Associate 
Administrator for Space Tracking and Data Systems to Deputy Director, JPL, 28 February 1983, "NASA 
Correspondence, 1983, pt. #1,"JPLPLC; JPL Annual Report, 1984, p. 13, and ibid., 1987, p. 41.JPLA. 

43. Memorandum, Lilley to CAMROC Project Office Members, HJune 1966, 18/1/AC 135, MITA. 

44. Renzetti 17 April 1992. 

45. Muhleman 8 April 1993. 

46. The ethane-methane ocean model of Titan was developed by Jonathan I. Lunine, David J. 
Stevenson, and Yuk L. Yung. See, for example, Lunine, Stevenson, and Yung, "Ethane Ocean on Titan," Science 
222(1983): 1229-1230. 



ONE STEP BEYOND 237 



hydrocarbons and nitriles, including ethane, methane, and acetylene. But Voyager 
revealed nothing about the moon's surface features. 47 

Titan's surface remained hidden from the view of radar astronomers, too. In 
February 1979, using the Arecibo S-band radar, Don Campbell, Gordon Pettengill, and 
Steve Ostro unsuccessfully attempted to detect Titan. Later, in 1987 and 1992, Dick 
Goldstein and Ray Jurgens also failed to receive echoes from Titan using the Goldstone 
Mars Station alone. 48 The bistatic Goldstone-VLA radar, however, promised an extra 
measure of sensitivity. 

Muhleman hoped to find land masses and challenge the ethane ocean model. He 
already had conducted a radio study of Titan, but that research had yielded ambiguous 
results. Muhleman teamed up with JPL radar astronomer Marty Slade, who oversaw oper- 
ation of the Goldstone half of the bistatic radar. Muhleman 's graduate students, Bryan 
Butler and Arie Grossman, participated in the experiments, too. In order to test the sys- 
tem, Muhleman, Slade, and Butler attempted a known target, the rings of Saturn, in the 
spring of 1988. The success encouraged them to attempt Titan. 49 

Muhleman, Butler, and Slade first observed Titan on the nights of 3, 4, 5, and 6 June 
1989 with the VLA in the so-called C configuration, in which the maximum separation 
among the 27 25-meter (82-ft) telescopes was about three km. The echoes were marginal, 
although those obtained on 4 June were strong, and the detection of 5 June was "quite 
certain." "The data," they concluded, "appear to favor a real variation in surface proper- 
ties but more observations are required." 50 

The backscatter from Titan was highly diffuse, similar to that from the Galilean 
satellites of Jupiter. The diffuse backscatter, they believed, was a strong argument against 
an ethane ocean being the reflecting medium. A liquid body without floating scatterers 
would be a specular not a diffuse reflector. Instead, the radar echoes from Titan suggest- 
ed an icy surface similar to that of Europa, Ganymede, or Callisto. The experiment, 
however, did not rule out entirely the existence of liquid hydrocarbons on Titan's surface 
that might exist in the form of small lakes. 

Muhleman, Slade, and Butler attempted Titan again in August 1992 and in the 
summer of 1993. 51 From these fresh echoes, they concluded that Titan does not always 
keep the same hemisphere towards Saturn, as had previously been believed. In addition, 
one region very bright to the radar consistently appeared 15 hours earlier than expected, 
suggesting that its rotational period was 49 minutes shorter than its orbital period of 
15.945 Earth days. 

More importantly, variations in radar reflectivity gave the first indications of surface 
conditions on Titan. Results from instruments on the Voyager spacecraft in the 1980s 
suggested that there might be a global ocean of liquid ethane. However, Muhleman, 
Slade, and Butler reported that only a few patches of liquid will be found by the European- 
built Huygens probe scheduled to land on Titan early in the next century after a journey 



47. Muhleman, Arie W. Grossman, Bryan J. Butler, and Slade, "Radar Reflectivity of Titan," Science 248 
(1990): 975-980. 

48. NAIC QR Ql/1979, 9; Campbell 8 December 1993; Goldstein and Jurgens, "DSN Observations of 
Titan,"in Posner.ed. The Telecommunications and Data Acquisition Report: Progress Report, Jan.-Mar. 1992 (Pasadena: 
JPL, 1992), pp. 377-379. 

49. Muhleman, G. Berge, and D. Rudy, "Microwave Emission from Titan and the Galilean Satellites," 
Bulletin of the American Astronomical Society 16 ( 1984) : 686; JPL Annual Report, 1988, p. 29, JPLA. 

50. Muhleman, Grossman, Butler, and Slade, "Radar Reflectivity of Titan," Science 248 (1990): 975-980, 
quote on p. 979. 

51. Muhleman, Grossman, Slade, and Butler, "Titan's Radar Reflectivity and Rotation," Bulletin of the 
American Astronomical Society 25 (1993): 1099; Butler, Muhleman, and Slade, "Results from 1992 and 1993 
VLA/Goldstone 3.5 cm Radar Results," ibid., p. 1040; GSSR Min. 19 February 1993. 



238 TO SEE THE UNSEEN 



aboard the Cassini spacecraft. The moon's surface seems to be covered mainly by icy 
continents, perhaps coated in tars of hydrocarbons. 

The results of Muhleman's radar research on Titan were of enormous interest to 
Dennis L. Matson, Cassini project scientist, and others involved in the planning of the 
Cassini mission. In 1989, NASA was preparing the Cassini Announcement of Opportunity 
for release on 1 December 1989. A major experiment on Cassini, as then planned, was a 
radar instrument to be built byJPL. The nature of Titan's surface was a major parameter 
in the design of any radar system for the Cassini mission. 

If an ocean of ethane and methane really covered Titan, the radar would have to be 
designed to anticipate the special scattering conditions that such a surface would create. 
The Goldstone-VLA radar data, then, would be useful in targeting the Huygens probe, 
and the targeting decisions had to be made before the launch of the Cassini spacecraft 
itself. 52 As Nick Renzetti characterized the situation: "So why put a $20 million radar on 
Cassini and get zilch? That really stirred the community for the last three years." 53 



The Polar Ice Caps of Mars 



The radar results from Titan were revealing but puzzling. The radar study of Titan 
also highlighted the continuing mission-oriented nature of radar astronomy. The same 
was true of Mars radar research. Although Muhleman intended to use the Goldstone-VLA 
bistatic radar primarily to study Titan, equally startling results came from its application 
to Mercury and Mars. The Goldstone-VLA system allowed radar astronomers to solve 
problems previously unsolved or solved unsatisfactorily. The Goldstone-VLA work added 
to a long tradition of studying Mars topography that began, as we saw in an earlier chap- 
ter, before Viking went to Mars, and continued in support of the Viking mission. Most of 
the Mars radar topography work done in the 1970s, in fact, related directly to Viking. 

The exploration of Martian topography and radar reflectivity from the 1970s into the 
1980s had yielded some rather interesting results. The studies done for Viking had 
revealed high roughness (large rms slopes) and sharp roughness transitions in the area 
around the Tharsis volcanoes and their associated lava flows. Tharsis itself was found to 
have a low overall reflectivity. The most unusual and controversial development was the 
claim by Stan Zisk and Peter Mouginis-Mark, from their analysis of Goldstone Mars data 
from 1971 and 1973, that the Solis Lacus region showed seasonal variations in its radar 
reflectivity which might indicate the presence of near-surface liquid water. 54 

The Tharsis and Syrtis Major regions were of special radar interest. Syrtis Major was 
a classical radar dark spot on Mars. From topographical data, George Downs showed that 
the Tharsis bulge was lower than originally thought. Geologists used the radar data to 
show that Tharsis had been tectonically inactive since the occurrence of the last major lava 
flows. Topographical data for the south Tharsis region suggested that it was an ancient 
impact basin. Interpretation of the radar studies of Downs and Simpson (at Arecibo) of 
the Syrtis Major area by USGS geologist Gerry Schaber indicated that it was a low-relief 



52. Muhleman to W. E. Giberson, 10 February 1989, and Memorandum, D. L. Matson to Dumas, 
8 January 1991, Renzetti materials. 

53. Renzetti 17 April 1992. 

54. Harmon, "Radar Observations of Mars and Mercury: History and Progress," paper read at the 
Thirtieth Anniversary Celebration of Planetary Radar Astronomy, 3 October 1991, Caltech; Zisk and P. J. 
Mouginis-Mark, "Anomalous Region on Mars: Implications for Near-Surface Liquid Water," Nature 288 (1980): 
735-738. See also Aaron P. Zent, Fraser P. Fanale, and Roth, "Possible Martian Brines: Radar Observations and 
Models, "Journal of Geophysical Research vol. 95, no. B9 (1990): 14,531-14,542. 



ONE STEP BEYOND 239 



shield volcano, rather than the impact basin it had always been believed to be, because it 
was not very heavily cratered. 55 

John Harmon arrived shortly after the installation of the Arecibo S-band radar as a 
Research Associate, after graduating from the University of California at San Diego with a 
doctoral thesis on solar winds. John Harmon began a series of studies of Mars topography 
and scattering, initially under the direction of Don Campbell, and drew the first topo- 
graphic profile of Syrtis Major. Starting in February 1980, Harmon and Steve Ostro under- 
took a study of Tharsis and the surrounding area using both the Arecibo S-band and the 
Goldstone X-band radars and taking data in both senses of circular polarization, in order 
to compare polarization ratios at both S-band and X-band. 

While the initial focus in 1980 had been on the Tharsis region, the 1982 observations 
took in a broader area and revealed correlations between maximum depolarization and 
the volcanic regions Tharsis and Elysium, while the heavily cratered upland terrain yield- 
ed relatively low depolarization. This led to the suggestion by Harmon and Ostro, and 
confirmed independently by radar astronomer Tommy Thompson and USGS Menlo Park 
geologist Henry J. Moore, who used Goldstone data, that most of the strong sources of dif- 
fuse and depolarized backscatter on Mars were rough-surfaced lava flows. 56 

Such was the state of radar studies of Martian topography and scattering, when 
Muhleman, Butler, and Slade began looking at Mars with the Goldstone-VLA bistatic radar 
in 1988. The proximity of Mars, in contrast to the great distance to Titan, allowed them 
to construct full-disk images of the planet. During the 1988 Mars opposition, moreover, 
the Earth and Mars were closer than they had been for 17 years. 

These images were not the product of radar range-Doppler techniques, but of stan- 
dard VLA radio astronomy imaging software. The array and its software avoided the prob- 
lem of north-south ambiguity that typically plagued planetary range-Doppler mapping; 
the VLA radio imaging software, which Muhleman regularly used in his planetary radio 
astronomy research, created unambiguous images. In this bistatic imaging mode, the 
Goldstone radar illuminated the target with a continuous-wave signal whose frequency was 
adjusted to remove the Doppler shift. When the VLA aimed at a target, the signal came 
from all over the planet, as though the target were a natural emitter of radio waves. Then 
the powerful imaging software of the VLA processed these echoes. 

Muhleman, Butler, and Slade observed Mars twice during the opposition of 1988 and 
three times during the opposition of 1992-1993. They obtained surface resolutions of 80 
km at the subradar point. The Mars observations differed from those of Titan, because for 
Mars the VLA A array (36-km maximum spacings) was used. The transmitted signal to 



55. Downs, Mouginis-Mark, Zisk, and Thompson, "New Radar-Derived Topography for the Northern 
Hemisphere of Mars," Journal of Geophysical Research 87 (1982): 9747-9754; Mouginis-Mark, Zisk, and Downs, 
"Ancient and Modern Slopes in the Tharsis Region of Mars," Nature 297 (1982): 546-550; Simpson, Tyler, 
Harmon, and Alan R. Peterfreund, "Radar Measurement of Small- Scale Surface Texture: Syrtis Major," Icarus 49 
(1982): 258-283; Schaber, "Syrtis Major: A Low-relief Volcanic Shield,"/<nmia/ of Geophysical Research 87 (1982): 
9852-9866; Roth, Downs, Saunders, and Schubert, "Radar Altimetry of South Tharsis, Mars," Icarus 42 (1980): 
287-316; R. A. Craddock, R. Greeley, and P. R. Christensen, "Evidence for an Ancient Impact Basin in Daedalia 
Planum, Mars," Journal of Geophysical Research 95 (1990): 10,729-10,741; Downs, R. Green, and Reichley, "Radar 
Studies of the Martian Surface at Centimeter Wavelengths: The 1975 Opposition," Icarus 33 (1978): 441-453; 
Roth, Saunders, Downs, and Schubert, "Radar Altimetry of Large Martian Craters," Icarus 79 (1989): 289-310. 

56. Harmon 15 March 1994; Harmon, Campbell, and Ostro, "Dual-Polarization Radar Observations of 
Mars: Tharsis and Environs," Icarus 52 (1982): 171-187; Harmon and Ostro, "Mars: Dual-Polarization Radar 
Observations with Extended Coverage," /caru$62 (1985): 110-128; Thompson and Henry J. Moore, "A Model for 
Depolarized Radar Echoes from Mars," Proceedings of the Lunar Planetary Science Conference 19th (1989): 409-422; 
Moore and Thompson, "A Radar-Echo Model of Mars," Proceedings of the Lunar Planetary Science Conference 21 
(1991): 457-472. Later radar mapping supported these observations: Muhleman, Butler, Grossman, Slade, and 

Jurgens, "Radar Images of Mars," Science 253 (1991): 1508-1513; Harmon, Michael P. Sulzer, Phillip J. Perillat, 
and Chandler, "Mars Radar Mapping: Strong Backscatter from the Elysium Basin and Outflow Channel," Icarus 
95 (1992): 153-156. 



240 TO SEE THE UNSEEN 



Mars was circularly polarized and both opposite circular and same circular echoes were 
received and mapped. As anticipated, the opposite circular echoes were dominated by the 
so-called specular (or phase-coherent) reflections. 

Muhleman and Butler found regions with anomalously high radar cross sections on 
Mars, particularly around the three Tharsis volcanoes and Olympus Mons. These, 
Muhleman recalled, '^just lit up like a Christmas tree." In contrast, the region west of 
Tharsis, extending over 2,000 km in the East-West direction and 500 km across at its widest 
point, displayed no cross section distinguishable from the noise in either polarization. 
"We didn't believe that result. We've never seen that on any real surface," Muhleman 
explained. 57 

Muhleman dubbed the area "Stealth," because it was invisible to the radar. 
Photographs do not indicate the nature of the Stealth region. Muhleman interpreted the 
lack of radar echo as arising from a deposit of ash or pumice spewed from the bordering 
Tharsis volcanoes and carried by winds blowing off the Tharsis ridge. He estimated that 
the Stealth material would have a density of less than about 0.5 grams per cubic centime- 
ter, be free of rocks larger than one centimeter across, and have a depth of at least five, if 
not ten, meters. 

Equally surprising was the radar signature of the residual southern polar ice cap. The 
1988 observations were made in the southern hemisphere around -24 latitude in late 
spring, so the seasonal carbon dioxide ice cap had sublimated away and exposed the resid- 
ual southern polar ice cap. That area had the highest radar cross section of any other area 
observed on the planet in 1988. Furthermore, the residual ice cap exhibited strong 
circular polarization inversion. Thus, unexpectedly, part of one of the terrestrial planets 
displayed radar characteristics more typical of the Galilean satellites. 

When Muhleman, Butler, and Slade looked at the VIA images, they "instantly saw 
that the brightest thing on the planet was the South pole, which turned out to be the 
residual South polar ice cap," Muhleman recalled. 'The amazing thing to us was that this 
ice was so reflecting, so bright, and its size was exactly the residual polar cap." 58 Also 
amazing was the fact that Dick Simpson and Len Tyler had failed to notice any unusual 
scattering properties from the North pole in data from a bistatic radar experiment 
conducted from the Viking spacecraft. 59 

Butler, Muhleman, and Slade again looked at Mars with the Goldstone-VLA radar 
during the 1992-1993 opposition, when the planet's North pole was visible from Earth. It 
was early northern spring on Mars, and much of the seasonal carbon dioxide polar ice cap 
was present. They were anxious to study the northern polar ice cap, but the ice was invis- 
ible to the radar. In stark contrast to the southern pole, no regions with enhanced radar 
cross sections appeared. "We still haven't figured that out," Muhleman admitted. "It's 
totally a mystery why we didn't find the residual North polar ice cap." 60 

The high radar cross section and polarization inversion of the Martian South polar 
ice cap were confirmed by observations made at the Arecibo Observatory during the 1988 
opposition by John Harmon, Marty Slade, and R. Scott Hudson. Hudson was a Caltech 
graduate student working on a doctoral degree in electrical engineering and had chosen 
aircraft radar imaging as his dissertation topic. Like those made by Harmon and Ostro in 



57. Muhleman 27 May 1994. 

58. Muhleman 27 May 1994. 

59. Muhleman 27 May 1994; Slade 24 May 1994; Muhleman, Butler, Grossman, and Slade, "Radar 
Images of Mars," Science 253 (1991): 1508-1513; Butler, "3.5-cm Radar Investigation of Mars and Mercury: 
Planetological Implications," Ph.D. diss., California Institute of Technology, 9 May 1994; Simpson and Tyler, 
"Viking Bistatic Radar Experiment: Summary of First-Order Results Emphasizing North Polar Data," Icarus 46 
(1981): 361-389. 

60. Muhleman 27 May 1994; Butler, "3.5-cm Radar Investigation;" Butler, Muhleman, and Slade, 
"Martian Polar Regions: 3.5 cm Radar Images," Lunar and Planetary Science Conference 25 ( 1994) : 211-212; Butler, 
Muhleman, and Slade, The Polar Regions of Mars: 3.5 cm Radar Images," Icarus submitted in May 1994. 



ONE STEP BEYOND 241 



1980 and 1982, these were monostatic, dual-polarization continuous-wave observations 
made with the Arecibo S-band and the Goldstone X-band radars. 

After obtaining promising results from a comparison of the 1988 data at both wave- 
lengths, an additional set of observations were made at S-band and X-band during the 
1990 opposition. Despite scheduling difficulties and the demands of competing types of 
radar observations (ranging observations for altimetry and mapping were also made at 
the two facilities), a good continuous-wave data set for S/X-band comparison was 
obtained in 1990. 

The Arecibo data confirmed the existence of Stealth. Using an algorithm developed 
by Scott Hudson and the Doppler spectra taken in the unexpected sense of polarization, 
they produced depolarized reflectivity maps that showed clearly the anomalously high 
radar reflectivity and polarization inversion of the residual South polar icecap. Hudson's 
algorithm allowed the investigators to use only Doppler spectra, without range measure- 
ments, to create a two-dimensional map of the Martian disk largely free of north-south 
ambiguity. 61 

Hudson's imaging technique was necessary in order to overcome the planet's over- 
spread nature. In comparison to Venus, Mars rotates rapidly on its axis and causes radar 
echoes from the limb (beyond the subradar area) to disperse broadly. The echo delay 
corresponding to the radius of Mars is 22.6 microseconds, which is much greater than the 
maximum interval of 0.725 microseconds needed to preserve complete spectral informa- 
tion over the band of frequencies present in the echo. As a result, when the computer 
samples signals, echoes from different ranges contaminate each other and become 
indistinguishable. Such radar targets are called "overspread." 

Arecibo scientists also had a technique for overcoming the overspread problem, but 
they were not motivated to apply it until the Goldstone-VLA results became known. 
Harmon explained: "Dewey Muhleman, with his VIA experiment, spurred us on to try 
and do better. I really hadn't been thinking about the overspreading problem. I probably 
should have; I should have been trying to figure out ways to get around it." 62 

Overspreading was a problem that ionospheric scientists had been dealing with for 
years, because the ionosphere is an extremely overspread target. Michael P. Sulzer, an 
ionosphericist at the Arecibo Observatory, solved the problem for the ionosphere by using 
non-repeating codes. Although Don Campbell at one time had asked Sulzer to think 
about applying the technique to Mars, no progress had been made until Harmon told 
Sulzer he was interested in trying the non-repeating code technique. 

Harmon then worked with Sulzer and Phil Perillat, who wrote the modified data- 
taking program. Normally, when a continuous-wave radar sends out a signal, the signal 
carries a code with a finite number of elements, and the code repeats at a regular inter- 
val. Harmon and Sulzer tested the non-repeating code, called alternately the "random 
code" or "coded long pulse" technique, and it worked the first time. Then Harmon wrote 
programs to do the data analysis. 

Harmon and Sulzer made their first random-code observations on 18 nights during 
the Mars opposition of September-December 1990 and created range-Doppler maps. 
Those maps, like all range-Doppler maps, included a north-south ambiguity around the 
Doppler equator. However, from eyeball comparisons with maps obtained early and late 
in the opposition, Harmon was able to resolve much of the ambiguity. 



61. Hudson, telephone conversation, 21 November 1994; Hudson and Ostro, "Doppler-Radar Imaging 
of Spherical Planetary Surfaces, "Journal of Geophysical Research 95 (1990): 10,947-10,963; Harmon, Slade, and 
Hudson, "Mars Radar Scattering: Arecibo/Goldstone Results at 12.6- and 3.5-cm Wavelengths," Icarus98 (1992): 
240-253. 

62. Harmon 15 March 1994. 



242 TO SEE THE UNSEEN 



The random-code maps confirmed the observations made with the Goldstone-VLA 
radar and revealed new information about the Elysium region, which Harmon had spent 
a long time studying in previous observations of Mars. Through those and subsequent 
observations made during the 1992-1993 opposition, he discovered strong depolarized 
radar echoes from the Elysium/Amazonis outflow channel complex. He interpreted the 
region, which was very young by Martian standards, as having lava flows that appeared to 
have partially filled pre-existing channels cut by flowing water. 63 

Mercury: Baked Alaska? 

The strange radar signature exhibited by the southern residual polar ice cap of Mars, 
reminiscent of the radar characteristics of the icy Galilean satellites of Jupiter, did not pre- 
pare Muhleman, Butler, and Slade for the surprising discovery of ice on Mercury. Mercury 
was simply too hot to support even the smallest ice deposit. Previous radar observations of 
Mercury had focused on scattering and topography and had not detected ice. 

Analysis of Mercury data taken between 1963 and 1965 at Goldstone, Haystack, and 
Arecibo snowed the planet to have a radar roughness 'Very similar" to that of the Moon. 
Dick Goldstein, from radar observations of Mercury made in 1969, started characterizing 
Mercury's topography. His work was the most detailed radar study of Mercury's surface 
prior to the Mariner 10 encounters and provided the first strong evidence for the exis- 
tence of craters on the surface. Dick Ingalls at Haystack and Don Campbell at Arecibo also 
found altitude variations on Mercury's surface from 1971 observations. Some of the ear- 
liest topographic radar studies of Mercury were carried out at Haystack by Bill Smith and 
Dick Ingalls. 64 

These early radar studies of Mercury were not linked to any specific NASA mission, 
but not because of any radar shortcomings. NASA made no meaningful effort to study 
Mercury until Mariner 10 flew by and photographed that planet in 1974-1975. The 
Mariner 10 photographs revealed a heavily cratered, lunar-like surface, as predicted by 
radar. Although Mariner 10 photographed over half of Mercury's surface during its flyby 
mission, it did not photograph any of the side not then exposed to the Sun's light and 
yielded only limited topographic information. Moreover, its flyby geometry prevented 
Mariner 10 from examining either pole directly. 65 

These gaps in Mercury coverage motivated a program of observations at Arecibo and 
Goldstone. John Harmon and Don Campbell, working in collaboration with Brown 
University geologists D. L. Bindschadler and James W. Head, carried out a campaign of 



63. Harmon 15 March 1994; NAIC QR Q2/1990, 7; Q4/1990, 7-8; and Ql/1991, 7; Ql/1993, 9; 
Harmon, Sulzer, and Perillat, "Mars Radar Mapping: Strong Depolarized Echoes from the Elysium/Amazonis 
Outflow Channel Complex," Lunar and Planetary Science Conference 22 (1991): 513. 

64. Muhleman, "Radar Scattering from Venus and Mercury at 12.5 cm," Journal of Research of the National 
Bureau of Standards, Section D: Radio Science 69D (1965): 1630-1631; Evans, Brockelman, Henry, Hyde, Kraft, W. 
A. Reid, and W. W. Smith, "Radio Echo Observations of Venus and Mercury at 23 cm Wavelength," The 
Astronomical fournaHO (1965): 486-501; Pettengill, Dyce, and Campbell, "Radar Measurements at 70 cm of Venus 
and Mercury," The Astronomical Journal 72 (1967): 330-337; Goldstein, "Mercury: Surface Features Observed dur- 
ing Radar Studies," Science 168 (1970): 467-469; Goldstein, "Radio and Radar Studies of Venus and Mercury," 
Radio Science5 (1970): 391-395; Goldstein, "Radar Observations of Mercury," The Astronomical Journal 76 (1971): 
1152-1154; Goldstein, "Review of Surface and Atmosphere Studies of Venus and Mercury," Icarus 17 (1972): 
571-575; Zohar and Goldstein, "Surface Features on Mercury," The Astronomical Journal 79 (1974): 85-91; Smith, 
Ingalls, Shapiro, and Ash, "Surface-Height Variations on Venus and Mercury," Radio Science 5 (1970): 411-423; 
Ingalls and Rainville, "Radar Measurements of Mercury: Topography and Scattering Characteristics at 3.8 cm," 
The Astronomical Journal 77 (1972): 185-190. 

65. Murray, Michael J. S. Belton, G. Edward Danielson, Merton E. Davies, Donald E. Gault, Hapke, 
Brian O'Leary, Robert G. Strom, Verner Suomi, and Newell Trask, "Mercury's Surface: Preliminary Description 
and Interpretation from Mariner 10 Pictures," Science 185 (1974): 169-179. 



ONE STEP BEYOND 243 



S-band radar observations of Mercury at Arecibo from 1978 to 1984. They measured 
Mercury's topography over much of the equatorial zone (between 12 North and 5 South 
latitude), an area not imaged by Mariner 10, and concluded that radar depths for large 
craters supported previous indications from photographs that Mercury's craters were shal- 
lower than lunar craters of the same size. 66 At the same time, Ray Jurgens, using the 
Goldstone S-band radar, started an ongoing series of Mercury observations to study the 
planet's topography and to correlate radar measurements with Mariner 10 visual images, 
in collaboration with geologists Gerald G. Schaber (USGS Flagstaff) and P. E. Clark 

GPL)- 67 

Such was the state of radar research on Mercury, when Muhleman, Butler, and Slade 

began their observations with the Goldstone-VLA bistatic radar during the inferior con- 
junction of August 1991. Although they made further observations during the inferior 
conjunctions of November 1992 and February 1994, the 1992 effort failed because of 
transmitter problems, and the 1994 data yet remains to be reduced. 68 The key results, 
then, were those from the 1991 observations. They did nothing less than revolutionize our 
knowledge of Mercury in a way that radar had not done since the discovery of the plan- 
et's 59-day spin rate by radar astronomers Gordon Pettengill and Rolf Dyce in 1965. 

During the first Goldstone-VLA observation of Mercury on 8 August 1991, Ray 
Jurgens coordinated activities at the Goldstone X-band transmitter, while Marty Slade and 
Bryan Butler awaited the echoes at the VLA, which was operating in the so-called A array, 
the most widely spaced configuration. During the 10 hours of observation, the VLA 
received in both senses of circular polarization. At the time of these observations, Mercury 
was at inferior conjunction and presented the hemisphere not photographed by Mariner 
10, roughly between 180 to 360, to the radar. As a result, the subradar point was far 
enough North to see over the North pole and into areas believed to be permanently shad- 
owed from the Sun. 

When Muhleman, Butler, and Slade looked at their results, they were astonished; 
they had found ice near Mercury's North pole. What signalled the presence of ice was the 
abnormal radar signature of the spot, which was unusually bright and showed a ratio of 
same circular to opposite circular polarization greater than unity, that is, a circular polar- 
ization inversion. This was the same type of radar signature displayed by Jupiter's Galilean 
moons. Muhleman recalled: "We instantly looked at the first image and saw this white spot 
on the North pole. We said, 'My God! Are we going to find an ice cap on every planet we 
look at?' This is crazy!" Marty Slade remembered looking at the bright spot and reacting: 
"It's not possible that could be ice! It's too hot!" 69 

Muhleman, Butler, and Slade again observed Mercury with the Goldstone-VLA radar 
two weeks later on 23 August 1991. This time, they transmitted both right-handed (RCP) 
and left-handed circular (LCP) polarization, and they received in both senses of polariza- 
tion for either sense, so that they could make all four correlations of the two polarizations 
(RCP to LCP, RCP to RCP, LCP to RCP, and LCP to LCP) . Mercury as seen from Earth had 
rotated 101. The subradar point was around 353 and the ice near the northern polar 



66. Harmon, Campbell, Bindschadler, Head, and Shapiro, "Radar Altimetry of Mercury: A Preliminary 
Analysis," Journal of Geophysical Research 91 (1986): 385-401. 

67. See, for example, P. E. Clark, M. E. Strobell, Schaber, and Jurgens, "Some New Radar-Derived 
Topographic Profiles of Mercury," Bulletin of the American Astronomical Society 16 (1984): 668; Clark, Jurgens, and 
M. Kobrick, "Analyses of Radar-Derived Topography and Scattering Properties of Mercury's Equatorial Region," 
Bulletin of the American Astronomical Society 17 (1985): 712; and Clark, M. A. Leake, Slade, Jurgens, Robinett, and 
C. Franck, "Scattering and Altimetry Measurements from Goldstone Radar Observations of Mercury in 1987," 
Bulletin of the American Astronomical Society 19 (1987): 863. 

68. Buder, "3.5-cm Radar Investigation," preface. 

69. Muhleman 27 May 1994; Slade 24 May 1994. 



244 TO SEE THE UNSEEN 



region still stood out brightly and exhibited polarization inversion. The researchers now 
knew that this was no fluke. 70 

Surprised by their own results, Muhleman, Slade, and Butler announced their results 
in two separate talks given on 6 November 1991 at the meeting of the AAS Division for 
Planetary Science, held in Palo Alto, California. 71 The scientific community greeted the 
news of their discovery with a fair amount of skepticism. 72 Prior to the launch of Mariner 
10, few had suggested the presence of ice on Mercury, and then for the wrong reasons. 
Some drawings of Mercury showed a white spot visible at the northern pole, and in 1974, 
on the eve of Mariner 10's first reconnaissance of Mercury, an atmospheric scientist had 
proposed that ice could have accumulated in the small planet's polar regions, perhaps in 
permanently shaded regions. 73 

The evidence for the presence of ice near Mercury's northern pole was based on an 
analogy between the radar signatures of known icy targets, the Galilean moons of Jupiter, 
and those found on Mercury. But more convincing evidence was needed, because Mariner 
10 had documented that planet's intense surface heat. The landscape was a parched 
wasteland of impact craters and volcanic plains, where midday temperatures soared to 
700 K, hot enough to melt lead. At the same time, though, Mariner 10's ultraviolet 
spectrometer had identified traces of hydrogen and oxygen in the tenuous atmosphere of 
Mercury. Project scientists had considered them to be remnants of the comets and aster- 
oids that periodically collide with the planet. 74 

While such collisions would explain the existence of water on Mercury, an explana- 
tion for the existence of a permanent water ice deposit on the planet came from a 
consideration of the geometry of Mercury's orbit. An impact crater could provide an area 
of permanent shade, provided that the geometry was just right. Mercury spins on its axis 
and rotates around the Sun in such a way that its equator always lies in the same plane as 
the Sun. As a result, neither pole ever sees more than a sliver of the Sun's disk above the 
horizon. On the other hand, the plane of Mercury's orbit about the Sun is inclined by 
seven degrees relative to that of the Earth, so that Earth-based radars can see into impact 
craters that are never directly illuminated by the Sun. 

David A. Paige and Stephen Wood of UCLA recomputed the thermal environment 
for Mercury's surface and concluded that the interior slopes of impact craters within five 
degrees of the poles would be cold enough to keep the loss of water ice through subli- 
mation at essentially zero. Other planetary scientists also began to argue for the existence 
of ice in craters on Mercury, and they suggested that craters on the Moon might also 
contain ice. As early as 1961, Kenneth Watson, Bruce C. Murray, and Harrison Brown had 
proposed that ice might exist in permanently shadowed craters near the lunar poles, but 



70. Slade, Butler, Muhleman, "Mercury Radar Imaging: Evidence for Polar Ice," Science 258 (23 October 
1992): 635-640; Butler, Muhleman, and Slade, "Mercury: Full-Disk Radar Images and the Detection and Stability 
of Ice at the North Pole, "Journal of Geophysical Research vol. 98, no. E8 (1993): 15,003-15,023. 

71. Slade, Butler, and Muhleman, "Mercury Goldstone-VLA Radar: Part I," Bulletin of the American 
Astronomical Society 23 (1991): 1197, and Buder, Muhleman, Slade, andjurgens, "Mercury Goldstone-VLA Radar. 
Part II," Ibid., p. 1200. 

72. David A. Paige, "Chance for Snowballs in Hell," Nature 369 (1994): 182; Chapman, "Ice Right 
Under the Sun," Nature 354 (1991): 504-505; J. Kelley Beatty, "Mercury's Cool Surprise," Sky & Telescope 83 
(January 1992): 35-36. 

73. Richard Baum, "Radar Bright, Ice Bright: V. A. Firsoff and Ice Caps on Mercury," Journal of the British 
Astronomical Association 103 (1993): 126 and 139; Firsoff, "Could Mercury have Ice Caps?" The Observatory 91 
(1971): 85-87; and G. E. Hunt, "There is no Evidence for Ice Caps on Mercury," The Observatory 92 (1972): 16; 
Beatty, "Mercury's Cool Surprise," Sky & Telescope 83 (1992): 35-36; Gary E. Thomas, "Mercury: Does its 
Atmosphere Contain Water?" Science 183 (1974): 1197-1198. 

74. Beatty, p. 36; Chapman, "Ice," p. 505; Chapman, Planets of Rock and Ice: From Mercury to the Moons of 
Saturn (New York: Scribner, 1982); and Faith Vilas, Chapman, and Matthews, eds., Mercury (Tucson: University 
of Arizona Press, 1988). 



ONE STEP BEYOND 245 



to date no lunar probe, not even the Clementine orbiter, has found any ice on the 
Moon. 75 A radar search at Arecibo also proved unsuccessful. 

Nick Stacy, a graduate student working on a thesis in radar astronomy under Don 
Campbell, looked for ice on the Moon with the Arecibo radar. Earlier, starting in 1982, 
Don Campbell and Peter Ford had carried out high-resolution range-Doppler imaging of 
the Moon and found no evidence of ice, but they were not looking for it Ford and 
Campbell brought the resolution of their images down from 300 to 150 meters, using the 
Higuillales antenna in a bistatic mode with the big dish. Stacy reduced the resolution to 
20 meters and aimed at the lunar poles. Unfortunately, the radar could not see far enough 
into the polar craters and detected no ice, though Stacy found some unusual scattering 
properties abound a number of lunar craters. 76 

Although the discovery of lunar crater ice remained elusive, John Harmon and 
Marty Slade at the Arecibo Observatory confirmed the existence of ice on Mercury. They 
imaged Mercury using the non-repeating code technique developed by Harmon and 
Mike Sulzer in order to overcome overspreading on Mars. These Arecibo images, accord- 
ing to David Paige, left "little room for doubt" about the presence of ice on Mercury. 77 

Soon after observing Mercury on 8 August 1991 with the Goldstone-VLA radar, 
Marty Slade travelled to the Arecibo Observatory to collaborate with Harmon on a dif- 
ferent set of Mercury observations. They acquired their initial data prior to 8 August 1991, 
on 28 separate dates during the periods 28 March to 21 April 1991, 31 July to 29 August 
1991, and 14 to 29 March 1992. During the spring 1991 observations, the subradar point 
of the Arecibo telescope subtended an area in the southern hemisphere of Mercury, while 
the summer 1991 observations covered a portion of the northern hemisphere, as the 
Goldstone-VLA had. The March 1992 data added to that already observed in the southern 
hemisphere. 

When Slade arrived at Arecibo, his first time at the observatory, Harmon had not yet 
analyzed the spring 1991 data; he had been too busy studying Mars data. Slade suggested 
to Harmon that they analyze the Mercury data and look for the icy radar signature near 
the North pole, which he, Muhleman, and Butler had just found with the Goldstone-VLA 
radar. According to Harmon, Slade said, "We think it's the pole; we're not sure." The 
Arecibo data confirmed the Goldstone-VLA discovery. There was no question of priority; 
Muhleman, Butler, and Slade discovered the ice on Mercury first, with the Goldstone-VLA 
radar. 

Harmon also examined the data collected from the southern hemisphere of 
Mercury in March-April 1991. "I saw a feature coming from what I figured probably had 
to be the South pole, because the latitude was about five degrees South [sic]," Harmon 
related. "I was pretty convinced it was coming from the South." 78 To confirm that the 
South pole was the source of the icy radar signature and not an artefact of north-south 
ambiguity, which would have shown a portion of the northern polar echo at the South 
pole, Harmon and Slade observed Mercury again in March 1992, when the subradar point 
was again in the southern hemisphere. The polar ice feature was seen again, confirming 
the presence of ice at the planet's South pole. 79 



75. Simpson 10 May 1994; Paige, Stephen E. Wood, and Ashwin R. Vaasavada, The Thermal Stability of 
Water Ice at the Poles of Mercury," Science 258 (1992): 643-646; Andrew P. Ingersoll, Tomas Svitek, and Murray, 
"Stability of Polar Frosts in Spherical Bowl-Shaped Craters on the Moon, Mercury, and Mars," Icarus 100 (1992): 
40-47; Kenneth Watson, Murray, and Harrison Brown, "The Behavior of Volatiles on the Lunar Surface, Journal 
of Geophysical Research 66 (1961): 3033-3045. 

76. Ford 3 October 1994; Campbell 10 March 1993; Campbell 8 December 1993; Stacy, "High- 
Resolution Synthetic Aperture Radar Observations of the Moon," Ph.D. diss., Cornell University, May 1993. 

77. Paige, "Chance for Snowballs in Hell," Nature 369 (1994): 182. 

78. Harmon 15 March 1994. 

79. Harmon 15 March 1994; Harmon and Slade, "Radar Mapping of Mercury: Full- Disk Images and 
Polar Anomalies," Scumce258 (1992): 640-642; Harmon and Slade, "An S-band Radar Anomaly at the North Pole 
of Mercury," Bulletin of the American Astronomical Society 23 (1991): 1121. 



246 TO SEE THE UNSEEN 



Next, Harmon and Slade proceeded to fit the radar results to photographic data 
from Mariner 10. Showing a correlation between a known crater and the radar ice would 
be persuasive confirmation of the discovery. Matching the northern polar radar ice loca- 
tion with a crater was hard; no Mariner 10 photographs were available for the entire 
region. Furthermore, the North polar radar anomaly was too large to fit within a single 
crater. The image, instead, appeared to consist of a number of crater-size (15-60 km in 
diameter) bright spots. Harmon and Slade plotted those features on a locating map cre- 
ated by NASA and the USGS and assigned letter labels to those features that lay in the pho- 
tographed hemisphere and to three prominent features in the unphotographed hemi- 
sphere. Many of the radar spots (8 out of 20) appeared to correspond to impact craters. 
Correlating the southern polar radar image with topography was simpler. The radar spot 
was entirely inside a crater called Chao Meng-Fu. 80 

The Goldstone-VLA and Arecibo images of Mercury once again highlighted how 
planetary radar astronomy often solves problems left unsolved or unsatisfactorily solved by 
optical techniques. The discovery of ice near Mercury's North and South poles, moreover, 
has inspired the European Space Agency to mount a major "keystone" mission to Mercury 
in search of polar ice, as well as a more modest-sized NASA Discovery flight. 81 

Radar astronomers also sought signs of anomalous radar signatures on other terres- 
trial planets. Muhleman, Butler, and Slade turned the Goldstone-VLA radar on Venus 
twice, 18 and 25 February 1990, receiving both senses of polarization in order to detect 
any peculiar polarization inversion, and made two maps. The maps had several striking 
features. Surprisingly, Alpha Regio had a high unexpected (depolarized or SC) reflectivi- 
ty on both maps and contained the second highest reflectivity values after Maxwell. On 
the second day's map, the point of highest reflectivity was in the Aphrodite region and was 
not visible in the previous map. On both maps, many very small areas, only a few pixels 
across, also had large unexpected (depolarized or SC) reflectivities, and some of them 
corresponded to mapped elevated areas such as Gula Mons, Sif Mons, and Bell Regio. 
Muhleman, Butler, and Slade concluded that a correlation existed between unexpected 
(depolarized or SC) reflectivities and elevation. Further bistatic observations of Venus in 
the spring of 1993 furnished fuel for another Muhleman graduate student, Albert 
Haldeman, to begin doctoral research, while Slade and Ray Jurgens also found highly 
reflective areas on Venus using just the Goldstone radar. 82 

Asteroids 

Throughout the 1980s and into the 1990s, the number of asteroids discovered and 
the number of publications dealing with asteroids grew at an unprecedented rate, at first 
as a result of the Palomar Planet-Crossing Asteroid Survey studies initiated in the 1970s, 
then as the number of asteroid researchers swelled. In 1932, an astronomer discovered 
the first Earth-crossing asteroid, 1862 Apollo. By 1994, about 200 Earth-crossing asteroids 
were known, more than half of which had been discovered in the previous seven years; yet 



80. Harmon, Slade, Velez, Andy Crespo, M. J. Dryer, andj. M.Johnson, "Radar Mapping of Mercury's 
Polar Anomalies," Nature. 369 (1994): 213-215; Harmon and Slade, "Radar Mapping of Mercury: Full-Disk 
Images and Polar Anomalies," Science 258 (1992): 640-643. 

81. Muhleman 24 May 1994; Paige, "Snowballs," p. 182. 

82. Slade 24 May 1994; K. A. Tryka, Muhleman, Butler, Berge, Slade, and Grossman, "Correlation of 
Multiple Reflections from the Venus Surface with Topography," Lunar Planetary Science 22 (1991): 1417; Jurgens, 
Slade, and Saunders, "Evidence for Highly Reflecting Materials on the Surface and Subsurface of Venus," Science 
240 (1988): 1021-1023; Butler, "3.5-cm Radar Investigation," passim; Slade 24 May 1994; and information pro- 
vided by Bryan J. Butler. 



ONE STEP BEYOND 



247 



the undiscovered population is huge. In the decade 1975-1985 alone, the total number 
of catalogued asteroids rose from 2,000 to more than 3,200. 83 

The field, as measured by the expanding literature, was undergoing the kind of swift 
growth that is typical of Big Science. Asteroid astronomy became a new theoretical frame- 
work with problems that radar astronomers sought to solve. Radar found its niche within 
asteroid astronomy because it could solve problems that other observational techniques 
could not do, namely, the creation of more accurate and reliable ephemerides and the 
imaging of asteroids. 

The focus of asteroid research was on near-Earth asteroids, although main belt 
objects remained of interest, too. Near-Earth asteroids, like meteorites, are thought to 
come primarily from mainbelt asteroids (Table 8). A large population of asteroids also 
cross the orbits of Earth and Mars. The term near-Earth asteroid usually means any aster- 
oid that can come close to the Earth, whether or not it crosses the orbit of the Earth. Eros, 
for example, crosses the orbit of Mars, but it is not an Earth-crossing asteroid and does not 
come near the Earth. Almost all of the near-Earth asteroids detected so far by radar are 
Earth-crossers. 



Table 8 
Asteroids Detected by Radar, 1968-1994 



12 



10 



8 



6 - 



4 - 



2 - 




O G* ^ 

c> o^ 2> 
o*> c> o> 



Data provided by Steve Ostro 



Mainbelt Asteroids 
Near-Earth Asteroids 



83. Ostro, Campbell, and Shapiro, "Mainbelt Asteroids: Dual- Polarization Radar Observations," Science 
229 (1985): 442. 



248 TO SEE THE UNSEEN 



The more interesting near-Earth asteroids also were better radar targets than main 
belt asteroids, because now and then they come closer to the Earth. With targets as small 
as asteroids, some only a kilometer or two in diameter, the distance to the target is critical 
to radar observations. The number of asteroids observed by radar astronomers grew 
rapidly during the 1980s because of the availability of radars with sufficient power and sen- 
sitivity to detect and study them. Another key factor in the growth of radar asteroid stud- 
ies was the decision of one radar astronomer, Steve Ostro, to begin studying asteroids 
almost exclusively. Quickly, his efforts dominated the asteroid study started at Arecibo and 
Goldstone in the 1970s. 

Before beginning this intense study of asteroids, Ostro had been making radar obser- 
vations of the Galilean moons and the rings of Saturn. In March 1979, about the time of 
Voyager's encounter with Jupiter, Ostro attended the third Tucson asteroid conference 
organized by Tom Gehrels. There, Ray Jurgens and Gordon Pettengill delivered a joint 
paper on radar observations of asteroids. The conference, especially the talks that placed 
the science of meteoritics and asteroid science in context with each other, gave Ostro the 
asteroid bug. He saw how the study of asteroids was essential to understanding the origin 
and evolution of the solar system. He also realized that radar was potentially the primary 
post-discovery technique for observing asteroids, and that asteroids, unlike planets and 
their moons, constitute a huge and diverse population. 84 

Later in 1979, his MIT dissertation completed, Ostro took a teaching position at 
Cornell University and began preparing a campaign of asteroid observations at Arecibo. 
The following year, he submitted his first NASA proposal for support of asteroid research. 
Echoing the work of Jurgens a few years earlier, Ostro laid out those asteroid opportuni- 
ties that would become available over the forthcoming decade at Arecibo, as well as the 
kinds of information he expected from his experiments. As targets, Ostro proposed three 
main belt asteroids (Iris in September 1980, Psyche in November 1980, and Vesta in 
February 1981) and two Earth-crossing asteroids (1862 Apollo in November 1980 and 
1915 Quetzalcoatl in March 1981). He planned to detect echoes from each target, esti- 
mate echo strength, and measure polarization, spectral bandwidth, and Doppler shift. 
From those four quantities, Ostro proposed to estimate asteroid size and rotation, place 
constraints on the composition and structure of asteroid surfaces, and improve knowl- 
edge of their orbital parameters. 85 

Over the following years, the estimation of asteroid physical properties and the deter- 
mination and refinement of their orbits remained fundamental aspects of Ostro's radar 
studies of asteroids. He systematically took range and Doppler data on all asteroids, as well 
as polarization measurements (receiving in both the expected and unexpected senses) in 
order to best estimate their surface roughness and structure. From measurements of the 
surface's reflectivity came estimates of the bulk density of the surface, its porosity, and rel- 
ative metallic composition. With each observation, Ostro tried to contribute to scientific 
knowledge about asteroids. 

Ostro also studied mainbelt asteroids. "Virtually every experiment gave an interest- 
ing result, and each radar signature was different," Ostro recalled. "Every single experi- 
ment was lucrative." 86 By 1992, Ostro had observed 28 near-Earth and 36 mainbelt 
asteroids. Between 1980 and 1985 alone, he made dual-polarization observations of 20 
mainbelt asteroids at Arecibo. These objects had low circular polarization ratios (the ratio 
of unexpected to expected echo power) ranging from about 0.00 to 0.40. The lowest 



84. Ostro 25 May 1994; Pettengill and Jurgens, "Radar Observations of Asteroids," in Gehrels and 
Matthews, pp. 206-211. 

85. Ostro 25 May 1994; Ostro, "Radar Investigations of Asteroids," proposal submitted to NASA in June 
1980 for support 1 November 1980 through 31 October 1981, Ostro materials. 

86. Ostro 25 May 1994. 



ONE STEP BEYOND 249 



value, 0.05 0.02 for the asteroid 2 Pallas, required that nearly all the echo arise from 
single-reflection backscattering from very smooth surface elements. 

"It became clear," Ostro explained, "that the mainbelt asteroids had a dispersion of 
reflectivities and polarization ratios. This was evidence for diversity in surface structure 
and in surface bulk density." 87 The data collected helped to characterize asteroid surfaces 
at scales between several centimeters and several kilometers and furnished constraints on 
surface bulk density and metal concentration, beyond those constraints obtained by 
optical methods. 

The metallic composition of the asteroids was an interesting question relating to pos- 
sible meteoritic analogues. The radar observations suggested wide variations in metal 
abundance, porosity, and decimeter-scale roughness on mainbelt asteroid surfaces, under- 
scoring the diversity of the asteroid population already evident from visible and infrared 
wavelength studies. Although the radar signatures of mainbelt asteroids required 
substantial surface roughness at some scale much larger than a meter, Ostro could not dis- 
cern the precise scale of this structure, much less the actual morphologies of surface 
features. Similarly, the radar albedos bolstered the hypothesis that metal concentrations 
on asteroids run the gamut. Serious questions remain, however, about detailed mineralo- 
gies, meteoritic associations, and evolutionary histories. 88 

"Each of the near-Earth asteroids is interesting in its own way," Ostro pointed out, 
"and still some interesting mysteries remain." 89 Echoes from the near-Earth asteroid 1986 
DA showed it to be significantly more reflective than other radar-detected asteroids. This 
result supported the hypothesis that 1986 DA was a piece of nickel-iron metal derived 
from the interior of a much larger object that melted, differentiated, and cooled, and 
subsequently was disrupted in a catastrophic collision. This two-kilometer-sized asteroid 
appeared smooth at centimeter to meter scales but extremely irregular at 10- to 100-meter 
scales. It might be (or have been part of) the parent body of some iron meteorites. The 
composition of asteroids thus bears directly on the question of their relationship to mete- 
orites, as well as the relationship between near-Earth and mainbelt asteroids. 90 

Starting in 1983, Steve Ostro began observing echo spectra with unusual shapes, 
including some spectra with double peaks (called bimodal). The first asteroid to show a 
bimodal spectra was 2201 Oljato, observed during 12-17 June 1983 at Arecibo. Asteroid 
astronomers had been discussing binary asteroids and contact-binary asteroids for a long 
time, but no evidence of their existence was at hand. 216 Kleopatra, a large mainbelt aster- 
oid, exhibited a strong bimodal echo spectrum. "That almost definitely is a contact bina- 
ry," Ostro explained. "But almost definitely is not definitely." 91 

Proof of the existence of binary and contact-binary asteroids eventually came from 
radar data. 92 Finding that proof was a problem left unsolved by optical and other research 
techniques. To the telescope, the biggest asteroid looks like a little dot, its shape indis- 
cernible. Radar succeeded in solving that problem through the development of new imag- 
ing and modeling techniques. The key to developing an appropriate technique, though, 
was to avoid simplistic models. Too, it was important that the asteroid approach Earth 
close enough to provide the Arecibo and Goldstone radars a sufficiently strong echo to 
resolve the target. 



87. Ostro 25 May 1994. 

88. Ostro, Campbell, and Shapiro, "Mainbelt Asteroids: Dual- Polarization Radar Observations," Science 
229 (1985): 442-446. 

89. Ostro 25 May 1994. 

90. Ostro, Campbell, Chandler, Hine, Hudson, Rosema, and Shapiro, "Asteroid 1096 DA: Radar 
Evidence for a Metallic Composition," Sdence252 (1991): 1399-1404. 

91. Ostro 25 May 1994. 

92. See, for example, the discussion in W. I. McLaughlin, "Radar Tracking of Asteroids," Sf>arf flight 34 
(1992): 167-169. 



250 TO SEE THE UNSEEN 



Ray Jurgens developed the first modelling technique for describing asteroid shapes 
in the 1970s. He applied it to spectral data from Eros. Steve Ostro applied Jurgens' triax- 
ial ellipsoid model to his 1980 and earlier 1972 Toro data and derived a rough description 
of the asteroid. 93 Similarly, when he applied Jurgens' model to the Earth-crossing asteroid 
2100 Ra-Shalom in 1981, Ostro found it to have a somewhat irregular shape. 94 

With researchers at Cornell, Ostro developed a different modelling technique, one 
that synthesized echo spectra acquired at different rotational phases of the asteroid into 
a convex envelope, called the hull, which represented the asteroid's silhouette as viewed 
from a pole. After he fit the hull model to Jurgens' Eros data, Ostro modeled the Earth- 
crossing asteroids 1627 Ivar and 1986 DA, observed in July 1985 and April 1986 at Arecibo. 
Interestingly, the hull estimates indicated that 1986 DA's hull was "extremely irregular, 
highly nonconvex, and possibly bifurcated." 95 

The case of 1986 DA suggested that any asteroid model had to accommodate the pos- 
sibility that the target might not be convex; both Jurgens' triaxial ellipsoid and the hull 
models were inadequate. Ostro also attempted to image asteroids with range-Doppler 
mapping techniques, beginning with 1627 Ivar in 1985. 

Range-Doppler mapping revealed a bimodal distribution of echo power, suggesting 
that the target was not convex. All previous images had relied exclusively on Doppler spec- 
tra data; these were the first range-resolved images of an asteroid. Nonetheless, they failed 
to define the asteroid's global shape. 96 

The next opportunity to attempt range-Doppler imaging came in 1988, with the 
close approach to Earth of the small asteroid 1980 PA. The technicians at Arecibo 
improved the telescope's data acquisition software and hardware, in order to improve 
resolution of the asteroid; the resolution of the Goldstone radar on the same target was 
still not fine enough. The Goldstone radar did not achieve the limit needed for radar 
asteroid observations until 1986, when the Voyager upgrades were completed. 97 

Ostro again attempted range-Doppler images, this time of 1989 PB, later known as 
4769 Castalia. On 9 August 1989, Eleanor Helin discovered the object on photographic 
plates taken at Palomar Observatory. Orbital calculations two days later showed that the 
asteroid would pass through the Arecibo Observatory's declination window during 
19-22 August and that at closest approach, Castalia would be only 0.027 astronomical 
units from Earth. These were ideal conditions for imaging the asteroid at Arecibo, though 
not so at Goldstone. Communications with Voyager 2, which was making its closest 
approach to Neptune, occupied the Goldstone 70-meter antenna; it was unavailable for 
use as a radar telescope until 30 August, when some observations of Castalia took place 
after closest approach. "At Goldstone," Ostro recalled, "everything was a disaster. We had 
an eight-hour track, and we got about 20 minutes of data." 98 

Getting time on the Arecibo antenna on such short notice (10 days after detection) 
was not a problem; Ostro already had time to observe Victoria, a mainbelt asteroid, which 
had shown a hint of a double-peak spectral structure in 1982. After doing a few runs on 



93. Ostro 25 May 1994; Ostro, Campbell, and Shapiro, "Radar Observations of Asteroid 1685 Toro," The 
Astronomical Journal 88 (1983): 565-576. 

94. Ostro, Alan W. Harris, Campbell, Shapiro, and James W. Young, "Radar and Photoelectric 
Observations of Asteroid 2100 Ra-Shalom," 7eanw60 (1984): 391-403. 

95. Ostro, Robert Connelly, and Leila Belkora, "Asteroid Shapes from Radar Echo Spectra: A New 
Theoretical Approach," Icarus 73 (1988): 15-24; Ostro, Rosema, and Jurgens, 'The Shape of Eros," Icarus 84 
(1990): 334-351; Ostro, Campbell, Chandler, Hine, Hudson, Rosema, and Shapiro, "Asteroid 1096 DA: Radar 
Evidence for a Metallic Composition," Science 252 (1991): 1399-1404, esp. pp. 1400-1401. 

96. Ostro 25 May 1994; Ostro, Campbell, Hine, Shapiro, Chandler, C. L. Werner, and Rosema, "Radar 
Images of Asteroid 1627 Ivar," The. Astronomical Journal 99 (1990): 2012-2018. 

97. Ostro 25 May 1994. 

98. Ostro 25 May 1994. 



ONE STEP BEYOND 



251 




Figure 38 

Range-Doppler radar images of Asteroid 1627 Ivar, 1985, made at the Arecibo Observatory by Steve Ostro. These are theferst 
radar images made of an asteroid. (Courtesy of Jet Propulsion Laboratory.) 

Victoria, Ostro spent the rest of the time on Castalia. "We saw CW [continuous-wave] 
echoes instantly," Ostro remembered. "A few of them from the first day looked strongly 
bifurcated." This was the first echo signature that said 'This is a contact binary." Although 
he had never claimed discovery of bifurcated asteroids in print, Ostro had seen the 
idiosyncratic radar signatures several times before." 

From the Doppler and range data, Ostro created 64 images of the asteroid with an 
average of two dozen pixels each. Each image was bifurcated and showed a bimodal 
distribution of echo power. Reading the sequence of images from left to right from top to 
bottom, one can see the asteroid rotate. 

When Ostro presented the images at the AAS Division for Planetary Science meeting 
a few months later, they attracted a dramatic intensity of attention; it was no less than the 
first time that anyone had resolved the shape of an asteroid from Earth. 'This was a major 
breakthrough, definitely a major breakthrough," Ostro reflected. 100 



99. Ostro 25 May 1994. 

100. Ostro 25 May 1994; Ostro, Chandler, Hine, Rose ma, Shapiro, and Yeomans, "Radar Images of 
Asteroid 1989 PB," Science 248 (1990): 1523-1528. 



252 TO SEE THE UNSEEN 



About a year after the imaging of Castalia, Scott Hudson started working on a math- 
ematical modelling technique to reconstruct the asteroid's shape in three dimensions. 
While still a Caltech graduate student, Hudson had worked with Ostro in developing a 
technique for creating planetary Doppler images free of north-south ambiguity. Hudson 
devised a complex mathematical model with 169 parameters in order to capture the shape 
of asteroid Castalia. The resultant three-dimensional model showed indisputably that the 
asteroid was bifurcated into two distinct, irregular, kilometer-sized lobes. 101 

Modelling three-dimensional asteroid shapes from radar data provided further evi- 
dence for the existence of asteroids with exotic shapes upon the approach of 1989 AC 
(later known as 4179 Toutatis), discovered in January 1989. Because of its extremely close 
approach to Earth, 9.4 lunar distances on 8 December 1992, Toutatis showed high 
promise as a candidate for imaging. Ostro proposed a Toutatis experiment to the NAIC 
and to Nick Renzetti, explaining how extraordinary the opportunity was and urging that 
Goldstone also make observations. 

Ostro planned to use both telescopes to take data in both senses of polarizations and 
to create range-Doppler images of several thousand pixels, considerably more resolution 
than had been achieved ever before. The high resolution was possible at Arecibo and 
Goldstone because of incremental improvements made in the data acquisition hardware 
and software over the preceding years. Ostro obtained continuous-wave echoes at 
Goldstone on 27 November, then range-Doppler images daily from 2-18 December 1992 
and at Arecibo each day from 13-19 December. In addition to the routine monostatic 
observations, Ostro's team took advantage of new antennas recently made available. They 
observed Toutatis bistatically with the DSS-14 transmitting and a new 34-meter beam- 
waveguide antenna (DSS-13) 21 km away receiving, and on one day they received with 
both DSS-14 and DSS-13 to acquire interferometric data. On yet another day, they col- 
lected data with the Goldstone-VLA radar. 

Preliminary analysis of the data showed Toutatis to have an unusually slow rotation 
rate and a maximum dimension of no less than 3.5 km. Interestingly, too, Toutatis 
appeared to consist of two irregularly-shaped components in close contact. The images 
provided a first glimpse of craters on an Earth-crossing asteroid, as well. The asteroid's 
roughness, as measured by the circular polarization ratio, indicated a considerable degree 
of general roughness at centimeter-to-decimeter scales, supporting the belief that Toutatis 
had undergone a complex collisional history. 



101. Hudson, telephone conversation, 21 November 1994; Ostro 25 May 1994; Hudson and Ostro, 
"Shape of Asteroid 4769 Castalia (1989 PB) from Inversion of Radar Images," Science 263 (1994): 940-943; 
Hudson and Ostro, "Doppler-Radar Imaging of Spherical Planetary Surfaces, "Journal of Geophysical Research 95 
(1990): 10,947-10,963. 



ONE STEP BEYOND 



253 




Figure 39 

Radar images of Asteroid 1989 PB (later known as 4769 Castalia). The asteroid's rotation is noticeable in the 64 images. 
(Courtesy of Jet Propulsion Laboratory.) 



254 



TO SEE THE UNSEEN 




Model of Asteroid 4769 Castalia. It was the first three-dimensional model of an asteroid ever produced. The picture shows 16 
different views of a three-dimensional model of Castalia, which is 1.8 km across at its widest. The model was created by Scott 
Hudson (Washington State University) and Steve Ostro ([PL) from data taken at Arecibo Observatory in 1989. (Courtesy of 
Jet Propulsion Laboratory, photo no. P43041A.) 

Since then, Scott Hudson has elaborated his model to recreate three-dimensional 
asteroid shapes. With Toutatis, he was dealing with over 1,000 parameters. The application 
of Hudson's reconstruction technique to the Toutatis images was complicated by the aster- 
oid's rotation. Unlike all other targets detected by radar, Toutatis was in a tumbling rota- 
tional state. 

At the 1994 AAS Division for Planetary Science meeting in November 1994, Ostro 
and Hudson presented several movies of Castalia, including one in which the asteroid was 
portrayed as it might be viewed in space, complete with fictional optical illumination. The 
use of the older Castalia data was on purpose; it suggested the potential rewards of using 
higher resolution data. In addition to Castalia and Toutatis, Ostro and Hudson began 
working in 1994 on three-dimensional modeling of 1620 Geographos, an asteroid which 
the ill-fated Department of Defense's Clementine spacecraft was scheduled to observe 
during a flyby mission. Although a computer malfunction prevented the Clementine 
encounter, Ostro captured a detailed sequence of Geographos images at Goldstone only 
days before the scheduled flyby. Subsequent modeling of the data has yielded an impres- 
sive simulation of an asteroid flyby. 102 



102. Ostro 25 May 1994; Hudson, telephone conversation, 21 November 1994; Ostro, Jurgens, Rosema, 
R. Winkler, D. Howard, R. Rose, Slade, Yeomans, Campbell, Perillat, Chandler, Shapiro, Hudson, P. Palmer, and 
I. de Pater, "Radar Imaging of Asteroid 4179 Toutatis," Bulletin of the American Astronomical Society 25 (1993): 1126. 



ONE STEP BEYOND 



255 




Figure 41 

Thf.se radar images of Toutatis repre- 
sent the highest resolution then 
achieved on an asteroid. A few impact 
craters, the first ever documented, are 
visible in the images. (Courtesy of Jet 
Propulsion Laboratory, photo no. 
P41525) 



The state-of-the-art imaging and modeling of Castalia, 
Toutatis, and Geographos are feats that only a spacecraft 
flying by an asteroid could match. Although no probe 
deliberately set out to photograph an asteroid, Galileo, on 
its voyage to Jupiter, sent back the first spacecraft images of 
an asteroid, mainbelt object 243 Gaspra, on 29 October 
1991 from a distance of about 16,200 km. Interestingly, 
Galileo also discovered that mainbelt asteroid 951 Ida had 
an orbiting satellite, recently named Dactyl. 103 

While the Toutatis images in themselves are spectacu- 
lar witnesses to the ability of radar astronomy to solve prob- 
lems left unsolved by other techniques, radar astronomy 
has achieved an equally great degree of success in another 
problem-solving area, asteroid orbits. Determining asteroid 
orbits with better degrees of accuracy and predictive relia- 
bility gained higher attention as scientists and the general 
public came to perceive asteroids as an ultimate threat to 
human civilization and to life itself on Earth. The percep- 
tion grew out of the work of nuclear physicist and Nobel 
laureate Luis Alvarez, who first proposed that an asteroid 
was responsible for the extinction of the dinosaurs some 
65 million years ago. Since then, evidence supporting the 
theory has accumulated, though not without arguments 
and evidence questioning the theory. 

In a seminal paper published in Nature, Clark 
Chapman and David Morrison argued that the probability 
of a kilometer-size asteroid hitting Earth in the next centu- 
ry was 1 in 5,000. The collision would have a global effect, 
regardless of the impact site, because the dust blasted into 
the stratosphere would end agriculture for several years. 
Billions of people would starve to death. 104 

In order to detect a potentially civilization- and life- 
threatening asteroid, the scientific community proposed 
Spaceguard, a network of six optical telescopes dedicated 
to detecting asteroids. The name Spaceguard came from 
the book Rendezvous with Rama, in which its author Arthur 
C. Clarke envisioned an asteroid striking Earth in northern 
Italy in the year 2077. In response to the impact's devasta- 
tion, the nations of Earth formed Project Spaceguard. 

Creating a real Spaceguard has not been so straight- 
forward. After asteroid 1989 FC came very close to the 
Earth in 1989, the American Institute of Aeronautics and 
Astronautics recommended to the House Committee on 
Science, Space, and Technology that it sponsor studies of 
asteroid detection and defense. Congress then commis- 
sioned NASA in 1990 to write reports on those subjects. 



103. The Spaceguard Survey: Report of the NASA International Near- 
Earth-Object Detection Workshop (Pasadena: JPL, 25 January 1992), p. 19; 
NASA Press Release 94-158, 20 September 1994, Renzetti materials. 

104. Chapman and Morrison, "Impacts on the Earth by Asteroids 
and Comets: Assessing the Hazard," Nature 367 (1994): 33-40. 



256 TO SEE THE UNSEEN 



NASA already had considered asteroid detection in a 1981 workshop held in Colorado, 
but 10 years later it acted in response to a Congressional mandate. The NASA 1991 work- 
shop brought together 24 asteroid scientists from around the world, including radar 
astronomer Steve Ostro. 105 

Although Congress has not yet funded Spaceguard, a battle over how to defend the 
planet against a "killer asteroid" rages. The recent collision of Comet Shoemaker-Levy 
with Jupiter has driven home the point that the planets, Earth included, are susceptible 
to potentially life threatening impacts from comets and asteroids. The Spaceguard 
proposal came along just as the Department of Defense was seeking post-Cold War appli- 
cations of its nuclear arsenal. The deflection of a menacing asteroid or comet with a series 
of nuclear explosions is, in the words of Carl Sagan and Steve Ostro, "a double-edged 
sword," which if wielded by the wrong hands could "introduce a new category of danger 
that dwarfs that posed by the objects themselves." They pointed out that a series of 
nuclear explosions capable of thwarting a dangerous asteroid is also capable of diverting 
a benign asteroid toward Earth. 106 

Regardless of the means used to defend Earth against asteroid hazards, radar is suit- 
ed to play a vital role in identifying potentially hazardous objects. Radar is ffe essential tool 
for astrometry (position and movement); it can determine asteroid orbits with greater 
accuracy and reliability than any other method. After the detection of an asteroid and the 
determination of its orbit, astronomers extrapolate the orbit into the future. Without 
radar precision measurement, the uncertainty of that extrapolation increases strikingly. 
The role of radar in Spaceguard, consequently, is as the primary, post-discovery ground- 
based technique for refining asteroid orbits. 

After Steve Ostro's experiences with the errors in the ephemerides provided for 1986 
DA and 1986 JK, he and fellow JPL employees Don Yeomans and Paul Chodas, who were 
in charge of calculating ephemerides for space missions, including those for a potential 
future asteroid flyby mission, assessed the extent to which radar observations could 
improve the accuracy of near-Earth asteroid ephemerides. They wanted to know how use- 
ful radar ranging was for refining the orbits of Earth-crossing asteroids. Could radar 
improve the extrapolation of asteroid orbits into the future? 

They studied four asteroids with different histories of optical and radar observations, 
1627 Ivar, 1986 DA, 1986 JK, and 1982 DB. The radar data provided only a modest 
absolute improvement for Ivar, which had a long history of optical astrometric data, but 
rather dramatic reductions in the future ephemeris uncertainties of asteroids having only 
short optical-data histories. Those improvements were impressive ones, to three orders of 
magnitude. 

Ray Jurgens, who had been observing asteroids at Goldstone since the 1970s, wrote 
a proposal to fund asteroid emphemeris work at JPL and persuaded Don Yeomans and 
Paul Chodas to help in the analysis of asteroid ephemerides. As Jurgens became over- 
whelmed by research and the rebuilding of the Goldstone radar, Steve Ostro took up the 
tasks of strengthening JPL's asteroid ephemeris program and advocating software tools 
and other measures for improving Goldstone's capability of detecting asteroids and 
improving the accuracy of asteroid orbit predictions. 107 



105. The Spaceguard Survey, pp. 1-3 and 49-52; Cunningham, pp. 1 13-1 16 and 141. 

106. Sagan and Ostro, "Dangers of Asteroid Deflection," Nature 368 (1994): 501. 

107. Ostro 25 May 1994; Yeomans, Ostro, and Paul W. Chodas, "Radar Astrometry of Near-Earth 
Asteroids," The Astronomical Journal 94 (1987): 189- 200; Ostro, The Role of Ground-Based Radar in Near-Earth 
Object Hazard Identification and Mitigation," in Hazards Due to Comets and Asteroids, in press, p. 9. For a summary 
of asteroid radar astrometry, see Ostro, Campbell, Chandler, Shapiro, Hine, Velez, Jurgens, Rosema, Winkler, 
and Yeomans, "Asteroid Radar Astrometry," The Astronomical Journal 102 (1991): 1490-1502; and Yeomans, 
Chodas, M. S. Keesey, Ostro, Chandler, and Shapiro, "Asteroid and Comet Orbits using Radar Data," The 
Astronomical Journal 103 (1992): 303-317. 



ONE STEP BEYOND 257 



The astrometric and imaging capabilities of radar soon will combine to reformulate 
the IAU circular that announces the discovery and orbit of a new asteroid. For newly 
spotted asteroids, Ostro has a vision of the kind of IAU circular that might be available 
before the end of the century. After astronomers discover and track an asteroid optically 
for a few nights and the orbit is at least crudely known, an IAU circular announces the 
object's existence. A few days later, the Arecibo or Goldstone radar observes the asteroid 
and takes range-Doppler data, refines the orbit, and images the object. The ephemeris is 
updated immediately. Streamlined software transforms the image data into a three-dimen- 
sional model of the asteroid, then produces a video simulation of the Sun-illuminated 
asteroid. This process yields a computer file that becomes the first post-discovery IAU 
circular: a finely-resolved video image of the object, as if made by a flyby spacecraft 
within a few days of discovery. 108 Here was the future of asteroid radar research and, to a 
dramatic degree, the future of planetary radar astronomy, as well. 



108. Ostro 25 May 1994. 



Conclusion 

W(h)ither Planetary 
Radar Astronomy? 

The dynamic interaction between epistemological (instruments and techniques) 
concerns and the kinds of problems radar astronomers seek to solve, which we have seen 
driving planetary radar astronomy to the present, also in all likelihood will continue to 
determine its future. Both new instruments and techniques will furnish the means for 
exploring new targets and for resolving problems, especially those left unresolved or 
unsatisfactorily resolved by optical means. 

Planetary radar techniques developed recently perhaps hint at the sources of future 
techniques. Three examples are John Harmon's non-repeating code, which he adapted 
from Arecibo ionospheric research; Dewey Muhleman's use of radio astronomy imaging 
and arraying techniques at the VLA, as part of the bistatic Goldstone-VLA radar; and the 
planetary imaging technique developed by Scott Hudson and Steve Ostro. The Harmon 
and Muhleman techniques reflect the continuing, though diminished, influence of iono- 
spheric research and radio astronomy on planetary radar astronomy. 

A surprising number of new instruments may be available, too, many through the 
grouping of either the Goldstone or Arecibo antenna in tandem with a radio telescope to 
form a bistatic radar. The Goldstone-VLA radar appears to point the way to additional 
combinations with the soon-to-be-completed Green Bank radio telescope, or perhaps to 
the Goldstone X-band radar in tandem with a tracking station in the Soviet Union. 
Already, the Russian Yevpatoriya tracking station has made bistatic observations of the 
asteroid Toutatis in conjunction with the Effelsberg radio telescope, though without 
achieving the impressive results of the Arecibo and Goldstone antennas. Politics and fund- 
ing will limit what, if any, future bistatic experiments take place outside the United States. 
Additional bistatic possibilities in the United States include the JPL Mars Station in com- 
bination with other Goldstone antennas, as well as an Arecibo-Goldstone link. 

The bistatic possibilities are not limitless, however; not inconsequential institutional, 
political, and budgetary obstacles aside, the elementary technological need for compatible 
transmitting and receiving frequencies limits many bistatic options. Even more limited is the 
creation of new radars. Other countries continue to build antennas, such as the Arecibo-size 
dish planned in Brazil, but none anticipate a radar capability. No facility dedicated entirely 
to planetary radar astronomy ever has been built; nonetheless, Steve Ostro believes that it is 
time to build one in order to study asteroids. The cost of designing and building such a 
radar observatory would approach the modest level budgeted for NASA's Discovery space 
missions. 1 The role of this facility in the Spaceguard project aside, its potential scientific 
value in a short period of time would exceed that of any one Discovery flyby of an asteroid. 
Time will tell whether this worthwhile and economical project is realized. 



1. Ostro 25 May 1994. 

259 



260 TO SEE THE UNSEEN 



These are all possible future planetary radar instruments. Nothing, especially not 
their scientific merit, either guarantees or favors their realization; budgets, not science, 
will determine their viability. With one exception, planetary radar astronomy always has 
subsisted on the budgetary margins, either by design (as at JPL) or by fate (as at Lincoln 
Laboratory) . As budgets are trimmed, the freedom to fund bistatic experiments from dis- 
cretionary funds diminishes, too. The only exception is Arecibo, where a five-year contract 
stabilizes the research budget, although within the shrinking NASA and NSF budgets. If 
one can say anything about the future of planetary radar astronomy with certainty, it is 
that the future is at the upgraded Arecibo telescope. 

The Arecibo upgrade, as well as the potentially available novel instruments and tech- 
niques mentioned above, will bring new research targets within the reach of radar 
astronomers. Among the most striking new targets visible to the upgraded Arecibo obser- 
vatory will be the satellites of Jupiter, lapetus, Rhea, Amalthea, Dione, and Hyperion. The 
detections of those bodies very well may lead to radar solving new scientific problems. In 
addition, the upgraded Arecibo telescope will be able to map Jupiter's Galilean moons at 
much higher resolutions, perhaps down to 100 kilometers, and uncover fresh facts regard- 
ing lo and Saturn's moon Titan. 2 

Planetary radar may contribute as well to our understanding of the terrestrial plan- 
ets through analysis of their polarization ratios; however, the greatest amount of research 
activity will be directed toward neither the terrestrial planets nor the systems of Jupiter 
and Saturn, but the asteroids. The space in which Earth turns abounds with thousands of 
asteroids. The largest, a kilometer or larger in diameter, number about 2,000, while those 
100 meters or more in diameter number 150,000 or more, and those 10 meters and 
larger amount to some 300,000,000. These are estimates of the asteroid population; the 
number of asteroids actually observed increases continually. The likelihood that one of 
those asteroids might approach Earth perilously close has heightened interest in them. 

In many ways, then, planetary radar astronomy has come full circle. It began with the 
study of large populations of meteors, and the observation and analysis of the large and 
varied asteroid population is carrying it into the future. Forty years ago, the forte of radar 
lay in its ability to determine accurately the radiants and speed of meteors and to 
ascertain unambiguously that they orbited around the Sun. Today, the value of radar is its 
ability to fix asteroid orbits with an accuracy and certainty that no other method can 
match. 

Current planetary radar techniques, however, can do much more with asteroids than 
the earliest radar investigators at Jodrell Bank and the Canadian National Research 
Council were able to do with meteors using their pioneering techniques and far less sen- 
sitive radar equipment. Today's planetary radar astronomers can characterize asteroid 
composition, size, and shape and can provide a unique imaging ability. The ever-growing 
number of asteroid targets, combined with this wide range of epistemological tools and 
the present societal interest in a potential "killer asteroid," guarantees that the future of 
planetary radar astronomy will be asteroid research. 

W(h)ither Planetary Radar Astronomy? 

Asteroid literature and funding have grown markedly over the last fifteen years. In 
the past, similar rapid growth in ionospheric and radio astronomy research carried 
forward planetary radar astronomy. This growth has not yet reached radar studies of aster- 
oids, however, and despite the expanding observational opportunities created by asteroid 
studies, the number of radar astronomers probably will not increase significantly. Steve 



2. Ostro, "Benefits of an Upgraded Arecibo Observatory," pp. 238-239; Ostro 25 May 1994; Campbell 
8 December 1993. 



W(H) ITHER PLANETARY RADAR ASTRONOMY? 261 



Ostro remains the sole full-time asteroid radar astronomer. Once the upgraded Arecibo 
radar becomes available, the number of radar investigators studying asteroids probably 
will increase, or rather, must increase, if an adequate number of observational opportuni- 
ties are to be seized. Already, the Arecibo Observatory has hired a planetary astronomer 
with an interest in asteroidsy 3 who will also take part in radar observations of asteroids. 
Don Campbell will participate in those observations, as too may Dick Simpson of Stanford. 
The growth in asteroid science, then, may shift current radar researchers into the field, 
rather than provide a basis for expanding planetary radar astronomy. 

As a scientific species, planetary radar astronomers have tended not to reproduce 
themselves. Hiring individuals from other fields yielded planetary radar astronomers in 
the 1960s and 1970s, but none in the last 15 years with the exceptions of Marty Slade at 
JPL and the recent hire at Arecibo. The number of planetary radar astronomers created 
through paid employment, therefore, may remain small and relatively stable. Being small 
yet may have its advantages in a future certain to be shaped by budget cuts in NASA and 
U.S. scientific research in general. 

The other traditional career path into radar astronomy, university training, may 
furnish fresh practitioners, though. Gordon Pettengill at MIT and Don Campbell at 
Cornell directed many radar astronomy dissertations, although certainly not all of those 
students entered the field. The MIT-Cornell axis has supplied planetary radar 
astronomers since the 1960s, but the last Ph.D. to enter the field through that route (Steve 
Ostro) graduated in 1978. Moreover, with the retirement of Pettengill at MIT and the 
approaching retirement of Campbell at Cornell, who will train future planetary radar 
astronomers at Arecibo? 

Outside of MIT and Cornell, only Caltech appears equipped or willing to train them. 
There, Dewey Muhleman has graduated one student, Bryan Butler, in 1994, who did 
doctoral research in radar astronomy. Although interested in pursuing radar research, 
Butler is at least equally excited by the prospect of planetary radio studies at the VIA, 
where he has taken a position. Muhleman is not interested in training additional radar 
astronomers. 

In contrast, Steve Ostro at JPL teaches a course on radar astronomy at Caltech. That 
position gives him the ability to both recruit and train future radar astronomers. The key 
to training future radar astronomers in an academic setting like MIT or Cornell remains 
the master-disciple relationship. Replacing Pettengill and Campbell, then, is Ostro, who is 
in a unique position to carry the MIT-Cornell alliance one step further by linking Caltech, 
JPL, and Goldstone to it. 

Ostro, a graduate of MIT who conducted his doctoral research on Cornell's Arecibo 
instrument, and a former member of the Cornell faculty, found Ray Jurgens and Marty 
Slade, graduates of the Cornell and MIT programs, respectively, when he began work at 
JPL. Ostro's arrival at JPL signalled a joining of the JPL and MIT-Cornell research groups. 
His opportunity to teach at Caltech and recruit radar astronomers, coming near the 
retirements of Pettengill and Campbell, assures the continuation of the master-disciple 
relationship as the source of future radar astronomers, but within a larger institutional 
(MIT, Cornell, CaltectvJPL) and instrumental complex that joins the Arecibo and 
Goldstone radars. The centering of Ostro within that complex also positions him to direct 
the future of radar astronomy. 

Like the number of practitioners, the radar astronomy literature will remain at a low 
level as a result of both the small number of researchers and the nature of the science 
reported in those publications. The discoveries to be made on the terrestrial planets and 
the moons of Jupiter and Saturn will not generate a substantial number of articles, 
because those discoveries likely will not merit that level of scientific attention. The results 



3. Harmon 15 March 1994. 



262 TO SEE THE UNSEEN 



of asteroid research, moreover, will be described in articles that discuss the characteristics 
of a substantial population of asteroids and not the properties of just one or two asteroids. 
Consequently, the number of asteroid-related publications will remain limited. 

Indeed, virtually the entire history of planetary radar astronomy has been one of 
limits. The number of practitioners has been limited, if not declining. As we saw, after the 
initial "explosion" of planetary radar activity in the early 1960s, as measured by the 
number of experimenters, publications, and instruments, the field of planetary radar 
astronomy assumed the manpower and publication dimensions of Little Science. After 
further shrinking during the 1970s, leaving a handful of researchers utilizing a single 
radar instrument in 1980, planetary radar astronomy stabilized at this lower level (the 
Arecibo radar being down for the duration of the upgrade) . The circumscribed number 
of opportunities to train future radar practitioners in academia, as well as retirements 
(most current practitioners are at or near retirement age), will keep manpower levels low. 



Little Science, Big Science 



The practice of planetary radar astronomy as Little Science in the instrumental and 
institutional context of Big Science will likely continue into the future. A number of 
factors integral to the field have confined planetary radar astronomy to its existence as 
Little Science. To begin with, the field generally has operated at the limits of the technol- 
ogy (the instrument hardware). As soon as an instrument became available, radar 
astronomers sought to discover what new targets it could detect. Once the farthest target 
was reached, and the spatial limits of research defined, radar astronomers had insufficient 
sensitivity to achieve more than a detection. Imaging planetary surfaces always involved 
pushing the instrument's signal-to-noise ratio and resolution capability to the limit. These 
restrictions in turn prompted radar astronomers to continually press for hardware modi- 
fications that provided incremental increases in sensitivity. In the end, though, what could 
be done was limited by the capability of the instrument. 

Another growth-limiting factor inherent in planetary radar astronomy is the avail- 
ability of targets, a factor intimately linked to instrument capability. The planets and their 
moons cannot be detected unless they are within radar range. The sensitivity limits of 
planetary radars, such as the Arecibo telescope, prevent investigators from observing 
targets except when they approach Earth. At other points in their orbits around the Sun, 
they are too far away for radars to detect them. Thus, Venus is observed at inferior 
conjunction and Mars at opposition. 

A related problem is that of declination. Although most planets rotate around the 
Sun more or less in the same plane, called the ecliptic, they are not visible in the sky at all 
times because of the Earth's motion about its own axis. A further complicating factor is 
the ability of the radar antenna to "see" a portion or all of the visible sky, that is, the 
so-called declination window of the antenna. The declination window of the Goldstone 
DSS-14 dish runs from 40 South to 80 North, while the Arecibo telescope is limited to 
solar system objects that pass within the far narrower band from 40 North to just below 
the equator. 4 

The combination of declination window and radar sensitivity restricts observational 
opportunities, so that planetary research demands only about five percent of total anten- 
na time. The finite number of planetary targets and the narrow observational windows 
also tend to limit the number of radar researchers. Thus, the tendency at Arecibo was to 
establish a given target as the terrain or turf of a particular researcher. The number of 
radar investigators at JPL was always too small for such a division of targets, although 



4. Renzetti, Thompson, and Slade, "Relative Planetary Radar Sensitivities: Arecibo and Goldstone," 
TDA Progress Report no. 42-94 (Pasadena: JPL, April-June 1988): 292. 



W(H) ITHER PLANETARY RADAR ASTRONOMY? 263 



during the 1970s Ray Jurgens "specialized" in Venus and asteroids and George Downs in 
Mars, with Dick Goldstein continuing to do a little of everything. 

The considerable and expanding number of known asteroids is too large for a single 
investigator. This will be especially true in the near future, once asteroid detection relies 
on CCD imaging and the Arecibo upgrade reaches completion. Then joining Ostro in 
radar observations of asteroids (many asteroid scientists hope) will be virtually all mem- 
bers of the small club of radar astronomy practitioners. Again, the expanded program of 
asteroid radar research that will take place throughout the remainder of this decade will 
not lead to a transformation of planetary radar astronomy into Big Science. 

Planetary radar astronomy has been and likely will remain Little Science embedded 
in the matrix of Big Science. John Krige's study of British nuclear physics research in the 
period right after World War II provides a different case of Little Science being conduct- 
ed with Big Science instruments. One can find another parallel example in the telegraph 
networks of the nineteenth-century United States. 

The Western Union telegraph company, formed by the merger of several separate 
companies, absorbed both of its principal rivals in 1866 to become one of the nation's 
largest companies and thereby created the largest electrical communication network in 
the world. While not Big Science, this was Big Business and Big Technology. By the very 
nature of their position in the company, telegraph operators had access to the large-scale 
technological laboratory formed by the telegraph lines. Just as access to technology led to 
the emergence of planetary radar astronomy, so access to the telegraph network led these 
operators to perform electrical experiments on the lines. Out of those experiments came 
numerous inventions, many of which were patented. 5 

It is not going too far to draw this parallel between Little Science (planetary radar 
astronomy) and Little Technology (telegraph inventors), for several reasons. For one, 
most radar astronomers were trained as electrical engineers, not scientists. Also, radar 
astronomy was a science driven by technology, namely, the availability of radars capable of 
planetary exploration. It was through these instruments and their associated techniques 
of analysis, not through direct sensory observation, that radar astronomers conducted 
their experiments. They analyzed not sensory experience, but wave patterns of electro- 
magnetic signals which analysis by computer software made "visible." Thus, not only were 
the instrumentation and techniques of radar astronomy dependent on technology, but so 
was the very content of the science. 

Planetary radar astronomy historically has remained at the intersection of science 
and engineering. Attendance of radar astronomers at both LAU and URSI meetings dur- 
ing the 1960s reflected the dichotomous nature of radar astronomy, perched between 
radio engineering (URSI) and astronomical science (IAU). The dichotomy arose from 
the fact that radar astronomy is a set of techniques (engineering) used to generate data 
whose interpretation yields answers to scientific (planetary astronomy and geology) ques- 
tions. Also as a result of this dichotomy, planetary radar astronomy concerns itself with two 
different but related sets of problems (in the Kuhnian sense discussed in Chapter Five). 
One set of problems is epistemological, that is, it deals with how radar astronomers know 
what they know and relates to the radar characteristics of the planets, such as surface scat- 
tering mechanisms, dielectric constants, and radar albedos; these problems arise out of 



5. For a careful scholarly study of telegraph operators as inventors, see Paul Israel, From Machine Shop 
to Industrial Laboratory: Telegraphy and the Changing Context of American Invention, 1830-1920 (Baltimore: Johns 
Hopkins University Press, 1992), which is based on the dissertation of the same title, Ph.D. diss., Rutgers 
University, 1989. For a discussion of the role of the entrepreneur in channeling the resources of large-scale 
organizations, specifically, the introduction of radio and radio research within the French military by Gustave 
Ferric, see A. Butrica, The Militarization of Technology in France: The Case of Electrotechnics, 1845-1914," 
paper read at the joint meeting of the American Historical Association and the History of Science Society, 
Cincinnati, December 1988. 



264 TO SEE THE UNSEEN 



the engineering side of radar astronomy. A second set of problems, such as planetary 
orbits and spin rates, arises out of the science side of the field. 

The rooting of Little Science (of Little Technology) within large technological sys- 
tems, such as the Western Union telegraph network or the Deep Space Network, suggests 
that it may be in the nature of large-scale "technosocial networks" or "systems" (to borrow 
the terminology of the social construction of technology mentioned in the Introduction) 
to sustain Little Science (or Little Technology) . Large technological systems form a uni- 
fied set of relations among individuals, objects, and ideas. As tightly "constructed" as these 
technosocial networks may be, the magnitude of the resources they encompass is of a suf- 
ficient extent to allow small-scale entrepreneurs (be they scientists, engineers, inventors) 
within the system to "socially construct" smaller technosocial networks within the larger. 

Without the larger technosocial network, then, the smaller network is unthinkable. 
Planetary radar astronomy simply would not have existed without the enormous, power- 
ful, highly sensitive radars on which the experiments were conducted and which were 
called into existence by the demands of the Cold War and Big Science. Another requisite, 
of course, was the radar experimenters themselves. The linking of research groups at MIT 
(Lincoln Laboratory), Cornell University, and (most recently) JPL (Caltech) has provid- 
ed a means by which the Little Science planted in the interstices of large technological sys- 
tems can perpetuate itself despite declining resources and limits to growth. For example, 
as planetary radar activity ceased at Haystack, it continued at the Arecibo Observatory. 
Given the symbiotic relationship between Big Science and the Little Science which 
depends on it, as well as the nature of that dependency, funding cutbacks intended to 
reduce Big Science also will diminish, or perhaps even eliminate, Little Science. Future 
research will have to determine how vast (and by what standard (s) that vastness is mea- 
sured) a technosocial network must be in order to sustain Little Science. 

The technological dependence of radar astronomy, and the availability of that tech- 
nology within large technological systems, thus accounts for the emergence of radar 
astronomy within Big Science settings. The technological dependence of planetary radar 
astronomy, however, does not explain its utilitarian proclivity, namely, the tendency of 
radar astronomers to justify their research by its usefulness to space exploration. Nor does 
the training of most radar astronomers as electrical engineers, who must think in both 
theoretical and practical terms at the same time, illuminate that tendency. The rise of 
radar astronomy concurrently with the creation and rapid growth of NASA was perhaps 
not coincidental. 

Although the space agency did not build research instruments outside NASA labo- 
ratories during the 1960s, its very existence from 1958 suggested the future availability of 
funds for instruments and research activity. The Endicott House Conference reflected 
those funding hopes. After 1970, when NASA funding became a reality, radar astronomy 
quickly began participating in NASA space missions, such as Viking, until radar astrono- 
my became a space project, the Magellan radar mission to Venus. This close relationship to 
NASA space missions certainly amplified whatever utilitarian bent radar astronomy 
already had. 

This utilitarian bent also arose from the very nature of conducting Little Science 
within the context of Big Science. Doing Little Science requires that scientists constantly 
defend the pragmatic value of their research. A good example is radar astronomy at JPL; 
it lived off the budgetary margins of NASA space missions until the 1980s. Because obtain- 
ing antenna time depended on securing the approval of a NASA mission, radar 
astronomers had to argue the value of their research on practical, mission-oriented terms. 



W(H) ITHER PLANETARY RADAR ASTRONOMY? 265 



In contrast, obtaining antenna time at the Arecibo Observatory depended on the sci- 
entific value of the radar experiment; its value to NASA was far less important, although 
research directly related to NASA space missions was carried out there. The primary dif- 
ference between the JPL and Arecibo facilities was the official recognition granted radar 
astronomy at Arecibo from the start. The Arecibo telescope always had radar astronomy 
as one of its prime research objectives, while the JPL Goldstone antenna served mainly to 
track NASA launches, not conduct scientific experiments. NASA recognition for the sci- 
entific value of the Goldstone radar dish has yet to be realized fully or even established on 
a permanent foundation, though some preliminary steps have been taken. 

We can conclude briefly the following about planetary radar astronomy. After a brief 
initial burst of activity, radar astronomy quickly developed the characteristics of Little 
Science in terms of manpower, instruments, and published literature. The field continued 
to shrink throughout the 1970s, reached a low plateau of activity around 1980, then rose 
slightly in the middle 1980s, as the Goldstone radar once again became available for 
research. 

A number of factors kept planetary radar astronomy a Little Science. Radar sensitiv- 
ity and target visibility within the declination window limited observational opportunities. 
The shortage of observational opportunities in turn restricted the number of investigators 
who could pursue radar astronomy on a full-time basis. Close ties to NASA space projects 
intensified radar astronomy's utilitarian tendency. The need to justify Little Science with- 
in a Big Science setting played at least an equal part in shaping that tendency. The case of 
the Arecibo Observatory, though, demonstrates the importance of securing institutional 
recognition for the conduct of Little Science from the outset. Finally, the subsistence of 
Little Science within Big Science niches and their symbiotic relationship may be a func- 
tion of large-scale technological systems, whether they be the Western Union telegraph 
network of the nineteenth century or the big dishes of twentieth-century radio astronomy 
and space communications. 



Planetary Radar Astronomy 
Publications 

At the beginning of this project, a bibliography of radar astronomy literature, con- 
sisting of 384 items arranged chronologically by year of publication and alphabetically by 
author within each year, was constructed from a search of the NASA STI Database (aero- 
nautics and space) and a published bibliography, Jean E. Britton and Paul E. Green, Jr., 
Radar Astronomy (Cambridge: MIT Lincoln Laboratory Library, 1962), which Mr. Green 
generously made available. The NASA STI Database search alone resulted in a printout of 
589 items published since 1963. To this initial bibliography were added additional publi- 
cations uncovered in the researching and writing of this book. 

The initial bibliography, with fewer than 400 entries, illustrated the diminutive char- 
acter of planetary radar astronomy. In comparison, the radio astronomy literature of just 
the past two decades measures in the thousands. Because the extent, as well as the devel- 
opment, of the literature might help to characterize the progress of planetary radar 
astronomy over several decades, the bibliography was pruned and grafted in such a way as 
to reflect the published literature. Dissertations were missing from the bibliography, while 
publications by foreign researchers and abstracts abounded. 

A number of rules were followed in including and excluding publications. Internal 
reports were omitted; these are not intended for consumption by the general public or 
the scientific community. Only works by American practitioners were included; British 
and Soviet titles were excluded. Planetary radar astronomy was defined more strictly than 
in the text; solar, lunar, meteor, auroral, and Earth radar studies; and synthetic radar aper- 
ture research were left out, because they are specializations unto themselves. Also exclud- 
ed were items dealing with hardware, instruments, or techniques and those providing 
interpretations of radar results by individuals outside the field. For example, an article on 
the interpretation of radar topographic data, whose first author was a planetary geologist, 
was left out; however, if the first author was a radar astronomer, the article was added. 
Finally, abstracts were excluded, dissertations included. 

The resulting planetary radar literature, spanning the period from 1958 to 1994 
inclusively, amounted to 272 entries, or an annual average of about seven. Only twice did 
15 or more items appear in a single year. A line chart (Table 9) showing the annual dis- 
tribution of planetary radar publications indicates the explosion of radar astronomy activ- 
ity during the 1960s. The remainder of the chart suggests the technological dependence 
of radar astronomy. A second spurt of growth appears following 1975, when the Arecibo 
Observatory S-band radar first became available, and a third spurt occurred around 1990, 
just after the Voyager upgrade of the Goldstone radar. 

When the annual publication numbers are grouped by 5-year intervals, the sharp 
peaks and valleys of the annual chart are smoothed out and a new trend emerges (Table 
10) . The volatile growth of the 1960s remains, but what appeared to be seesaw-like growth 
around 1975 and 1990 disappears. Instead, a dip replaces the growth following 1975, and 
the literature reaches a plateau of activity. This plateau suggests that since 1980 the field 
has reached the limits to its growth. 



267 



268 



TO SEE THE UNSEEN 



Table 9 
Planetary Radar Astronomy Publications 




Annual Distribution 



Table 10 
Planetary Radar Astronomy Publications 



60 -, 




1990 



By 5-Year Interval 



A Note on Sources 

For the early history of radar astronomy, a number of archival sources were consult- 
ed. The Historical Archives, U.S. Army Communications-Electronics Command, Ft. 
Monmouth, NJ, have several boxes of material on the pioneering lunar radar work of John 
DeWitt, but no such archival material was found on the radar work of Zoltan Bay, with the 
exception of the documents in the possession of his widow. The Naval Research 
Laboratory Historical Reference Collection, Office of the Historian, was not a ready 
source of information on the lunar radar work carried out there; much of the 
Laboratory's records remain classified. In contrast, the archives of Jodrell Bank, housed 
at the University of Manchester, contain a wealth of open information on radar astrono- 
my, and a computerized index is available. 

Radar research on meteors began at Stanford University as early as the 1950s. The 
university archives, however, hold no records relevant to either the early or later work 
done there. The only records available are those of the Stanford Center for Radar 
Astronomy, which for the most part consist of a large collection of offprints that document 
the Center's research results. Von Eshleman, the Center's director, was a far more impor- 
tant source of documentation. 

Records relating to radar astronomy at the Arecibo Observatory are located for the 
most part in filing cabinets at the National Astronomy and Ionosphere Center (NAIC) 
offices on the Cornell University campus and are not normally open to researchers. 
Among the most useful of those records are the quarterly reports to the NSF and copies 
of Center for Radiophysics and Space Research (CRSR) research publications. The NAIC 
library retains copies of dissertations completed at the Arecibo Observatory. The CRSR, 
located in the same building, has the earlier ARPA reports. The library of the Arecibo 
Observatory contains additional reports, program plans, dissertations, and other materi- 
als. The minutes of the open sessions of the National Science Board were helpful, as were 
the archives of the AFCRL at Phillips Laboratory, Hanscom AFB, although the amount of 
documentation at each place was lean. 

In contrast, an overwhelming abundance of documents relating to the history of 
radar astronom